Experiments and Exercises for Chemistry Courses - #4

Searching for Chemicals:  A Material Science Lesson for Chemistry Students.  Part 1

This Exercise is #4 in Experiments and Exercises in Chemistry Courses
(see end note 1)
For more web sites by Steven Murov including chemistry sites, jump to http://murov.info

Textbooks written for high school and college chemistry courses contain coverage of a wide range of chemistry topics.  For some purposes, less is better and it can be argued that broad coverage can result in less overall learning.  A careful assessment and prioritization of topics should be performed and texts pared down to the essentials that are needed for continued learning.  On the other hand, there are some very important topics that are commonly given insufficient attention.  The basics of climate change and the threat posed by climate change should be included in every chemistry course (e. g., please visit: http://murov.info/climatemod.htm).  Polymers, metals and metal alloys surrounds us in our daily lives but receive minimal attention in the typical chemistry course. 

Chemistry laboratory experiences tend to emphasize identification of substances and verification of identification using properties.  In contrast, very few courses consider the challenges of the selection of materials and determination of properties needed for various applications.  This kind of challenge can be very stimulating, instructive and provides valuable insight into chemistry not necessarily provided by traditional chemistry approaches.  To address the shortcomings on some of these topics, this three part lesson (see:  http://murov.info/chemexpts.htm ) has been designed to provide a brief experience with selection of materials for various applications with an emphasis on polymers and metal alloys.  The first lesson has been designed primarily to provide familiarity with sources of information and provide exercises on traditional problems like finding properties of compounds or identifying compounds given some properties.  The second lesson provides some examples of the search for chemicals for specific applications.  This author admittedly has very limited expertise in the field of material science so any corrections and suggestions will be considered and appreciated. 

The discussions in this site have been divided into three categories.  The first two categories are covered in many sources and are included here to provide more experience and as a review  The third category (Part 2) or the search for materials based on desired properties has not received adequate exposure and is the primary purpose for the development of these sites.  A Part 3 has been more recently added.

Bull and Roberts Lab, 1914      File:Bull & Roberts Lab 1914.jpg - Wikimedia Commons

I.  The determination of properties of substances

II.  Identification of substances from properties.

III.  Searches for materials based on desired properties.  Jump to http://murov.info/matsci2.htm

Appendix A.  The Properties of Substances (Elements, Compounds)

Appendix B.  The Properties of Solvents

Appendix C.   Search for Compounds from Properties 

Appendix D.  Spectra of Substances

Appendix E.  Links to Information about Metal Alloys

Appendix F.  Solutions to Problems

I.  The determination of properties of substances
Given a substance, there are many approaches that can be used to determine the literature values of the properties of the substance.  A couple of decades ago, the starting point was often the Handbook of Chemistry and Physics, the Dictionary of Organic Compounds or the Merck Index.  While these resources are still valuable sources of information, the three books mentioned are large and cumbersome to carry around. With smart phone access to the Internet, it is often possible to find properties very quickly using one of several available web sites.  Appendix A contains hot links to many of these sites.  However, use all Internet sites with caution as many contain a huge collection of data and errors are not uncommon.  The exercises in this section have been designed to provide an introductory experience with some of the sites that provide properties of substances.  For the first section on elements, any of the many periodic table sites often will provide sufficient information.  For the properties of compounds, experience with the sites listed in Appendix A is the best educational pathway to acquire an understanding of the usefulness of the sites.

1. Physical Data.  In 1869 when Dimitri Mendeleev published a periodic table that has survived over 150 years, only 63 of the currently discovered elements (118) had been discovered.  Mendeleev arranged the elements according to increasing atomic mass but started new groups with each of the alkali metals as he found that in doing so, the elements in vertical columns had properties similar to the other elements in the group (e.g., lithium, sodium, potassium, rubidium and cesium all react violently with water to produce hydrogen gas and a basic solution).  To sort the elements according to reactivity properties, Mendeleev brilliantly left spaces in his chart for elements not yet discovered so that elements that followed aligned with similar elements above and below them.  For two of the empty element spaces, Mendeleev confidently named the elements eka aluminum and eka silicon after the elements above the spaces in his table.  See the image below.  Based on the properties of the surrounding elements, Mendeleev predicted properties for eka-aluminum and eka-silicon (see table below). Fill in the missing spaces in the table and comment on the accuracy of Mendeleev's predictions.
Useful resources:  http://www.knowledgedoor.com/      https://www.webelements.com/ (under binary compounds)   

  Table 1-A-1 filled in.   

3.  Properties of oxygen:  Fill in the table for the properties of oxygen.
(filled in table I-A-3)

a.  The image shows the pouring of liquid oxygen through a magnetic field.  a.  What do you observe? 
(Answer at II-A-3-a)

b.  The Lewis structure to the right satisfies the rules for the drawing of a Lewis structure.  Does the structure explain the behavior of liquid oxygen in a magnetic field.  If not, is it possible to draw a Lewis structure for oxygen that follows Lewis structure guidelines?  (Answer I-A-3-b))

While there is overlap, the questions below have been divided into several categories:  physical properties, chemical properties, isotopes, isomers and toxicity.

2.  Which of three is water?  (I-B-2 for answer)

Amazingly, of the millions of known substances, water is probably the only substance where you have observed the solid and liquid in a container and probably accept its behavior as normal.  But think about this situation:  as the temperature drops to the freezing point, should the liquid expand or contract (should the density increase with decreasing temperature or increase?).  Hopefully, you responded that the volume of the liquid should decrease with cooling resulting in an increase in density (density = mass/volume).  A decrease in volume increases the density as the mass does not change.  If this contraction continues with freezing, the solid should have a higher density than the liquid and it should sink in its liquid state.  This is the expected behavior and it is realized like the 2nd and 3rd test tubes for almost all substances except for water.  The conclusion then is that water must be in the first tube since its density behavior is very uncommon resulting in the ice floating in liquid water. 

3.  If water behaved like almost all other substances, what would happen to lakes in freezing weather?  (I-B-3 for ans.)

4.  The behavior of the density of states of water as a function of temperature is shown in the graph below Suggest a reason for the unusual behavior of the density of water at its melting point.  http://murov.info/EM-st1.pdf, Murov, S. J. Chem. Ed., 2013, 90, 1484-5.  "Liquid-Solid Density:  Observations and Demonstrations."  (Cover) http://pubs.acs.org/toc/jceda8/90/11   https://pubs.acs.org/doi/10.1021/ed300162x .  
(I-B-4 for answer)

C.  Chemical properties.  Octane ratings for automotive gasoline are often based on arbitrarily setting the "knocking" performance of 
2,2,4-trimethylpentane at 100 and n-heptane at 0.  Knocking occurs when the combustion rate of the gasoline is not optimal for the engine.  100 is generally good and 0 means a lot of knocking.  If the octane of a sample is rated 87, it knocks at the same rate as an 87:13 mixture of 2,2,4-trimethylpentane and n-heptane.  Prefix iso is used for those isomeric (same formula) alkanes in which one methyl group is attached to the next to end carbon atom (second last) of the continuous chain.  Using this system, 2-methylheptane can be called iso-octane.  The fuel industry has named 2,2,4-trimethylpentane "isooctane". 

1. Is this proper use of the prefix iso and if not, what is the problem with this use?
(I-C-1 for answer)

As a result of polymer chemistry, we are surrounded by objects made out of many different kinds of plastics.  In the 1967 classic movie, The Graduate, the following conversation was heard between the main character, Benjamin Braddock (portrayed by Dustin Hoffman, a 29 year-old playing a 21 year-old in his film debut), the guests and a family friend, Mr. McGuire, at Ben’s college graduation party:

Guests: We're all so proud of you, proud, proud, proud, proud, proud, proud, proud. What are you going to do now?
Ben: I was going to go upstairs for a minute.
Guests: I meant with your future, your life.
Ben: Well, that's a little hard to say.
Mr. McGuire: I just want to say one word to you - just one word.
Ben: Yes sir.
Mr. McGuire: Are you listening?
Ben: Yes I am.
Mr. McGuire: 'Plastics.'
Ben: Exactly how do you mean?
Mr. McGuire: There's a great future in plastics. Think about it. Will you think about it?
Ben: Yes I will.
Mr. McGuire: Shh! Enough said. That's a deal.

Styrofoam is one of the many commonly used plastics.  Among many uses, it is found in fast food containers and shipping containers.  Styrofoam is a form of polystyrene and is made by polymerizing styrene.  The essential part of styrene for the polymerization process is the C=C double bond.  If a hydrogen is in the place of the phenyl (benzene ring), polyethylene is the resulting polymer and if the benzene ring is replaced by a methyl, polypropylene is the resulting polymer. 

2.  If the benzene ring is replaced by a chlorine, draw a short segment of the resulting polymer that can be formed and name some of its uses. (I-C-2 for answer)

3,  Nitrogen dioxide is one of the dangerous pollutants in smog.  In an internal combustion engine, air introduced causes the reaction (combustion) of oxygen with gasoline.  Air is 78% nitrogen, 21% oxygen and almost 1% argon.  The heat of combustion raises the temperature in the cylinder to the point that the oxygen can react with nitrogen producing nitrogen monoxide (nitric oxide).  The nitric oxide eventually reacts with more oxygen to produce NO₂. 
a.  Write equations for the formation of NO and NO₂ and draw a Lewis structure for NO₂.  (I-C-3-a for answer)

c.  Given the opportunity, NO₂ tends to partially dimerize to N₂O₄.  Draw the Lewis structure of N₂O₄ including formal charges and suggest an explanation for the dimerization not going to completion.
(I-C-3-c for answer)

4.  The three penicillin structures shown above are amoxicillin, ampicillin and penicillin G.  Penicillin G was serendipitously discovered by Alexander Fleming in 1928 but it was not until the urgency of WWII infections that a method for delivering penicillin was developed.  Unfortunately, penicillin G is not stable in stomach acid and has to be injected to be effective.  While injections are vastly superior to no treatment for bacterial infections, chemists and pharmacologists were successful with their research efforts to modify the penicillin structure so that it would be stable in stomach acid.  Amoxicillin and ampicillin are two of the results of the research and are still commonly used today to treat infections.

a.  What change common to both molecules was made to penicillin G to make amoxicillin and ampicillin?  (I-C-4-a for answer).

b.  Why does this change make the penicillin derivatives stable in acid?  (I-C-4-b for answer)

c.  Could the researchers have been sure that the structural change would not decrease antibiotic activity?  Explain your answer.  (I-C-4-c for answer)

1.  Consider the properties of water and heavy water.  Are there significant differences and are the differences explainable from isotopic differences?  Is the density difference consistent with the mass difference?  (I-D-1 for answer)

2.  Do you think it would be safe to drink heavy water?  (I-D-2 for answer)

https://www.dovepress.com/review-of-deutetrabenazine-a-novel-treatment-for-chorea-associated-wit-peer-reviewed-fulltext-article-DDDT
https://pubs.acs.org/doi/10.1021/acs.biochem.7b00765
https://pubmed.ncbi.nlm.nih.gov/25069517/

The two primary isotopes of uranium found on earth are shown below along with the nuclear reactions for radioactive decay.  U-235 undergoes fission when impacted by neutrons and is used in nuclear reactors and bombs.  U-238 does not undergo fission but can be converted to fissionable Pu-239.  The problem is that U-238 composes 99.7% of naturally occurring uranium.  For uranium to be fissionable, it must contain much higher than 0.3% U-235.  Because isotopes have very similar physical and chemical properties, it is difficult and expensive to enrich uranium enough to make it fissionable.  The enrichment process was one of the reasons for the Iranian treaty which regulated the amount of enrichment.  However, the U.S. pulled out of the treaty giving Iran more leeway in enrichment.

3.  Write a nuclear reaction for the fission of U-235.  (I-D-3 for answer)

E.   Isomers are compounds with the same formula but differ structurally in some way.  For instance, 2-methylpropane (isobutane) is a structural isomer of n-butane.  Because of the structural differences, the chemical and physical properties of isomers usually differ sometimes substantially.  Stereoisomers are not necessarily easy to distinguish but play a very important role in nature.

Geometric isomers are a type of stereoisomer that usually differ by the orientation of the groups attached to a double bond.  The figure to the right show the geometric isomers (2nd and 3rd structures) of dichlorethane and also a structural isomer.  Because rotation around a double bond does not occur at room temperature, the geometric isomers can be distinguished and separated.  One very important application of this 11-cis trans isomerism occurs in the eye and enables vision.  Energy from light causes 11-cis retinal to isomerize to all-trans retinal resulting in a signal to the brain that results in vision. 

1. Use an analogy to a lock and key to explain how conversion of
11-cis retinal to all-trans retinal could result in rejection of the key from the lock. (I-E-1 for answer)

An even more subtle form of stereoisomerism occurs when two compounds are mirror images that are not superimposable.  There are many extremely important examples in nature where this type of isomerism occurs including the sugar family and the amino acids used to form polypeptides and proteins.  Non-superimposable mirror images have many identical physical properties but differ in the way they rotate polarized light and importantly, the way they interact with other stereoisomers.

An example that you might have encountered is that the primary components of caraway and spearmint oil are d-carvone and l-carvone respectively that are mirror images of each other.  The two isomers fit into different sites in the nose resulting in different odors perceived by the brain with d-carvone giving a caraway odor and l-carvone a spearmint odor. 

2.  Compare the properties of the two carvones and comment on similarities and differences.  Are the differences experimental or real?  For more information, please visit:
S. L. Murov and M. Pickering, J. Chem. Ed., 50, 74 (1973).  "The Odor of Optical Isomers - An Experiment in Organic Chemistry."   https://pubs.acs.org/doi/10.1021/ed050p74   (I-E-2 for answer)

F.  Toxicity. 

1.  For the compounds listed, record the oral LD₅₀ values for rats and calculate the amount that would kill half the population of 70 kg humans assuming that the extrapolation is valid.
(source Appendix A-2-b.  I-F-1 for answer)

https://www.slideserve.com/noelani/environmental-hazards-and-human-health slide 37 

2.  Would you consider vanillin to be a safe food additive? Explain your answer.  (I-F-2 for answer)

3.  Acetaminophen is the active ingredient in “non-aspirin” pain relievers. Extra strength tablets contain 500 mg of acetaminophen. How many tablets would be toxic to half the population of 70 kg humans (assuming the rat LD₅₀ values apply to humans)?   (I-F-3 for answer)

4.  https://www.slideserve.com/noelani/environmental-hazards-and-human-health  slide 37 Dioxin is a by product of bleached paper production.  For a disaster involving dixoin, please visit:
https://www.theatlantic.com/photo/2014/12/bhopal-the-worlds-worst-industrial-disaster-30-years-later/100864/.  Often environmentalists urge the replacement of plastic food plates with paper plates.  Is this clearly a good way forward?  Explain your answer.  (I-F-4 for answer)

5.  The venom of black widows has a rat LD₅₀ of approximately 0.002 mg/kg and rattlesnake venom has an LD₅₀ of about 0.5 mg/kg.  Assuming a density of 1 g/mL, what volume of venom do black widows and rattlesnakes have to inject to have a 50% chance of killing a 70 kg human? What are the many assumptions that go into this calculation? Does the amount intuitively seem like a reasonable amount for a spider bite?  (I-F-5 for answer)

See:  https://en.wikipedia.org/wiki/Pathophysiology_of_spider_bites 
https://pubmed.ncbi.nlm.nih.gov/3775789/ 
https://untamedscience.com/blog/worlds-deadliest-snakes/  
https://biochem-molbio.imedpub.com/determination-of-lethal-dose-ld50of-venom-of-four-different-poisonoussnakes-found-in-pakistan.php?aid=21045

II.   Identification of substances from properties.

The sites in this section includer problem solving experience by providing physical properties, ir, nmr and or mass spectra.  This is a small selection of those available on the Internet. There are also many instructional sites available that teach students how to solve problems and interpret spectra.  Searches for instructional sites are left to the user.  The first part of the exercise involves the solving of unknowns given some physical properties and limited spectral information.  Appendix C has several sites that can be used to assist with this assignment.  Inputting the information into the sites will yield possible hits.  It is sometimes easier to solve these challenges without the assistance of the
Appendix C sites.

Searching for Unknowns. Use one or more of the sites (this part of the exercise was designed for use with the Organic Chemistry Data Base  (https://www.colby.edu/chemistry/cmp/cmp.html)  from Appendix C to find the best matches to the information provided in each question below. Of the sites in Appendix C, it is the best for inputting refractive index information.  The site, http://murov.info/orgcmpds.htm also includes refractive indices and has sortable columns.  The possible compounds list that results depends on which web site is used.  Those listed in the answers are results from the Organic Chemistry Data Base.  For the three cases where there are multiple possibilities, suggest a method for distinguishing among them.  (Filled in table at II.)

For more exercises with many spectra included, please visit:
http://murov.info/orglab/51-x5.pdf
http://www3.nd.edu/~smithgrp/structure/workbook.html
https://www.orgchemboulder.com/Spectroscopy/Problems/index.shtml
https://webspectra.chem.ucla.edu/
http://chemistry.miamioh.edu/organicspecid/
http://alpha.lasalle.edu/~price/202 COMBINED SPECTROSCOPY PROBLEMS.pdf 

 1. Elements - Periodic Tables -
      WebElements - http://www.webelements.com/  
      http://murov.info/aufbaupt.htm     http://murov.info/periodictables.htm
      http://murov.info/pertabtrends.htm                 http://murov.info/pertabtrends.pptx
       Directory of Periodic Tables - https://www.meta-synthesis.com/webbook/35_pt/pt_database.php?Button=All
                                                 http://murov.info/periodictables.htm 
       Periodic table with history of elements - http://elements.vanderkrogt.net/
       Chronology of the development of the periodic table - http://murov.info/timelines.htm
       History of elements and periodic table - http://www.chem.unt.edu/~jimm/REDISCOVERY%207-09-2018/
       Properties of the elements -  http://www.knowledgedoor.com/
            https://material-properties.org/prices-of-chemical-elements-kg/
            https://dbpedia.org/page/Prices_of_chemical_elements  
2.  Compounds - Properties

         a. Tabulation
            Murov - http://murov.info/orgcmpds.htm
            WolframAlpha - http://www.wolframalpha.com/
            Chemical Book - http://www.chemicalbook.com/
            Chemidplus - https://chem.nlm.nih.gov/chemidplus/    https://chem.nlm.nih.gov/chemidplus/chemidlite.jsp
            Stenutz - http://www.stenutz.eu/chem/search.php
            ChemBK - https://www.chembk.com/en
            Knovel Critical Tables (If using Explorer, it must be newest version)
                  (21824 compounds in sortable tables) - login required  -  
                   initial registration or login:  https://app.knovel.com/web/register.v ,
                        already registered login:  https://app.knovel.com/web/login.v ,                   
                  click on or copy and paste:   
                  https://app.knovel.com/web/view/itable/show.v/rcid:kpKCTE000X/cid:kt002VLXT1/viewerType:itble/
                  To filter the listing, click on the triangle following the desirred parameter,
                   select filter and then enter the limits of the desired parameter (<, > or =) and hit enter.
                   (7274 Compounds in sortable tables) - 
                    https://app.knovel.com/web/view/itable/show.v/rcid:kpKS000009/cid:kt00395F16/viewerType:itble/
            ChemSynthesis - https://www.chemsynthesis.com/
            Kaye and Laby -
                   organic -https://web.archive.org/web/20190519191800/http://www.kayelaby.npl.co.uk/chemistry/3_3/3_3.html
                   inorganic - https://web.archive.org/web/20190502165701/http://www.kayelaby.npl.co.uk/chemistry/3_2/3_2.html 
            Chemland 21 - http://www.chemicalland21.com/listaz01.htm
            Chemblink http://www.chemblink.com/
            ChemSRC - https://www.chemsrc.com/en/
            LookChem - http://www.lookchem.com/
            Human Metabolome Database - http://www.hmdb.ca/  
            EPA - https://chemview.epa.gov/chemview
                      https://www.epa.gov/saferchoice
            MolBase - http://www.molbase.com/
            PubChem - https://pubchem.ncbi.nlm.nih.gov/
            Osha - https://www.osha.gov/chemicaldata/
            Shriner, et.al, Systematic Identification of Organic Compounds, manual for identifying organic compounds especially
                  with the use of derivatives, includes tables of common organic compounds with melting or boiling points
                  and melting points of derivatives in tables at back.               
            https://celqusb.files.wordpress.com/2018/04/kupdf-com_systematic-identification-of-organic-compounds-wiley-shrinerhermannmorrillcurtinfuson.pdf

    b.. Tabulation + MSDS
            Acros, Fisher - https://www.fishersci.com/us/en/brands/I9C8LQ1I/acros-organics.html
            Alpha Chemical  - https://www.alfa.com/en/chemicals/
            ChemExper Chem. Directory -  http://www.chemexper.com/ 
            Chemidplus -  https://chem.nlm.nih.gov/chemidplus/    https://chem.nlm.nih.gov/chemidplus/chemidlite.jsp
            Chemindex - http://ccinfoweb.ccohs.ca/chemindex/search.html
            Chemspider - http://www.chemspider.com/
                                http://www.chemspider.com/SimpleSearch.aspx
            EMD Chemicals - http://www.emdmillipore.com/US/en/documents/Z.qb.qB.tecAAAFDDJUsznLq,nav
            TCI America - http://www.tcichemicals.com/en/us/support-download/brochure/catalog.html  
            Wikipedia - https://en.wikipedia.org/wiki/Dictionary_of_chemical_formulas
                             https://en.wikipedia.org/wiki/List_of_inorganic_compounds
            Chemical Book - http://www.chemicalbook.com/ 

     c.  MSDS or SDS 
             Aldrich, Sigma,- https://www.sigmaaldrich.com/united-states.html
            MSDS Solutions - http://www.msds.com/ 
            Vermont Safety Information Resources, Inc. - http://hazard.com/msds/ 
            MSDSprovider - http://www.msdsprovider.com/  
            MSDS online - https://www.msdsonline.com/     
            MSDS digital - https://www.msdsdigital.com/msds-database
            Fisher - https://www.fishersci.com/us/en/catalog/search/sdshome.html
            EHSO - http://ehso.com/msds-sds.php 

Appendix B.    Solvent Properties
        http://murov.info/orgsolvents.htm     http://murov.info/orgsolvsort.htm
        https://www.organicdivision.org/ama/orig/organic_solvents.html  
        http://www.stenutz.eu/chem/
        http://www.wiredchemist.com/chemistry/data/physical_character_solvents.html 
        https://www2.chemistry.msu.edu/faculty/reusch/OrgPage/solvent.htm
        https://www.sigmaaldrich.com/chemistry/stockroom-reagents/learning-center/technical-library/solvent-properties.html
        https://en.wikipedia.org/wiki/Solvent
        https://www.ch.ic.ac.uk/williams/Solvent%20properties.pdf
        Knovel Critical Tables (If using Explorer, it must be newest version)
                  (21824 compounds in sortable tables) - login required  -  initial registration or login:
                  https://app.knovel.com/web/register.v , already registered login:
                  https://app.knovel.com/web/login.v ,
                  click on or copy and paste: 
                  https://app.knovel.com/web/view/itable/show.v/rcid:kpKCTE000X/cid:kt002VLY34/viewerType:itble/
                    To filter the listing, click on the triangle following the desirred parameter, select filter
                       and then enter the limits of the desired parameter (<, > or =) and hit enter.
        ChemSynthesis - https://www.chemsynthesis.com/
        nmr of deuterated solvents 
            http://www.wiredchemist.com/chemistry/data/common_nmr_solvents.html 
            http://www2.chem.umd.edu/nmr/reference/isotope_solvent.pdf 

  (Iodine) Like all of the halogens, the most common oxidation state of iodine in compounds is -1 and they form 1:1 compounds (e.g. KI) with the alkali metals.  Tellurium properties are not consistent with those of the other halogens.  The halogens behave as non-metals but tellurium has both metal and non-metal properties.

• Properties of halogens.
• They all form acids when combined with hydrogen.
• They are diatomic molecules in their elemental states.
• They are all fairly toxic.
• They readily combine with metals to form salts.
• They are highly reactive and electronegative.

 

 

I-A-3.  Properties of oxygen:  Filled in the table for the properties of oxygen.

Property	boiling point (K)	melting point (K)	allotropes	Lewis structures of O2
	90.2	54.4	O, O2, O3, O4  atomic oxygen, dioxygen, ozone, tetraoxygen

 

I-A-3-a. The image shows that the liquid oxygen bends towards one of the magnetic poles.

I-A-3-b.  The first Lewis structure of O₂ shown fits all the Lewis structure guidelines.  The second one does not satisfy the octet rule and therefore would not be favored as the correct structure since the first structure does satisfy the rules.  However, the first structure has all paired electrons and would not result in the magnetic behavior observed.  The second structure does have unpaired electrons and is more consistent with the observation.  This is a very rare case where the favored Lewis structure is apparently not a good model for the molecule.

 

 

I-B-1. 

Compound/Property	Formula	molecular mass (g/mole)	common name	m.p. (oC)	b.p. (oC)	density (sold) (g/cm3)	density (liquid) (g/cm3)   25oC	refractive index	LD50 (mg/Kg)
acetic acid	C2H4O2	60.05	X	16.6	117.9	1.26 (17oC)	1.049	1.2717	X
acetaminophen	C8H9NO2	151.2	tylenol	168	420	1.293	X	X	1944
amoxicillin	C16H19N3O5S	365,41	X	194	743	1.6	X	1.702	>1.5x104
d-carvone (S)	C10H14O	150,22	X	25.2	231	X	0.963	1.497	X
l-carvone (R)	C10H14O	150.22	X	25.2	231	X	0.963	1.497	X
dideuterium monoxide	D2O	20.03	heavy water	3.8	101.4	1.106 (11.06oC)	1.107	1.328	X
dihydrogen monoxide	H2O	18.02	water	0.00	100.00	0.916      (0oC)	0.998	1.333	X
dioxin	C12H4Cl4O2	321.97	X	305	X	1.8	X	1.437	2x10-2
nitrogen dioxide	NO2	46.01	X	-9.3	21.1	X	X	1.449	X
penicillin G	C16H18N2O4S	334.4	benzylpenicillin	217	X	1.4	X	1.69	8x103
11-cis-retinal	C20H28O	284.44	X	64	X	X	X	X	X
all trans-retinal	C20H28O	284.44	X	61	421	0.948	X	X	X
styrene	C8H8	104.15	X	-31	145	X	0.909	1.516	2650
2,2,4-trimethylpentane	C8H18	113.13	isooctane	107.4	99	X	0.692	1.391	5000
uranium -235	U	235.04	X
uranium-238	U	238.08	X	1132	4132	18.7			750
vanillin	C8H8O3	166.18	X	81	285	1.06	X	1.587	1580

I-B-2.  The one on the left is water as ice floats in liquid water.

I-B-3.  Since it is coldest at the top of the lake where the water is exposed to ambient temperature, the water would freeze at the surface but then sink as the ice would be denser than liquid water.  This process would repeat until the lake filled with ice.  This would make the lake very inhospitable to most life as we know it so we are fortunate that water behaves anomalously.

 

I-B-4.  As can be observed in the images, hydrogen bonding results in ice having a very fixed structure the the water molecules farther apart than they are in liquid water.

 I-C-1.  Use of isooctane as the name for 2,2,4-trimethylpentane violates the rule for the meaning of "iso" and can lead to confusion and error.

I-C-2.

Uses:  pipes, medical devices, wire and cable insulation, window frames,
 drainage pipe, water service pipe, medical devices, blood  storage bags, and many more.

 

 

 

I-C-3-a.    N₂  +  O₂  =  2 NO       2 NO  +  O₂  =  2 NO₂  

I-C-3-b.   As the Lewis structure of NO₂ correctly shows, NO₂ is a free radical.  There is a strongly energetic drive for free radicals to react and form a product with all paired electrons. 

I-C-3-c.  The free radicals are very reactive but when formal charges are added to the Lewis structure of N₂O₄ to the right, there are adjacent + charges on the nitrogen atoms and negative charges on two nearby oxygens.  These repulsive forces destabilize the molecule and make the dimerization energetically close to neutral.

I-C-4-a.    An -NH₂ group was added.

II-C-4-b.  The amino group, -NH₂ like ammonia is a Brönsted base and accepts protons in acidic media.  The presence of the NH₂ in amoxicillin (and ampicillin) enables the molecule to accept a proton in the acidic stomach and become a relatively stable cation.

I-C-4-c.  Any change to a structure can affect the properties.  It is like making a minor change to a key.  It probably will no longer fit the lock and work.  However, in the case of penicillin, the change apparently does not affect the part of the molecule that fits correctly into the active site.  Both ampicillin and amoxicillin retain the antibiotic properties and for most bacteria are even more effective than for penicillin G.

I-D-1.  The melting and boiling points for heavy water are about 3.8 and 1.4 C^o higher.  Since the atomic mass of D₂O is about 11% higher than for H₂O, these differences are not surprising.  For isotopes of other elements, the mass percent differences are much lower and most chemical and physical properties are similar.  Assuming the sizes of the two molecules are the same, the density of D₂O should be 11% higher than for H₂O.  This is exactly what is observed.  For hydrogen, the mass difference can result in significant rate differences up to a factor of about seven if the breaking of a bond to the H or D is involved in a rate determining step.  For an example of the effect of the isotope substitution on stretching frequencies, please see:  http://murov.info/orglab/50-x4.pdf .

I-D-2.  Do you think it would be safe to drink heavy water?  A human can tolerate up to about 20% heavy water but a higher percentage can cause problems with about 50% being lethal.  As reaction rates change with deuterium substitution, the biochemistry of the human body can be dangerously altered by too much heavy water.  see:  https://sciencenotes.org/can-you-drink-heavy-water-is-it-safe/

I-D-3

 

 

 

I-E-1.  If a slight change is made to a key (e.g. 11-cis-retinal), the key will no longer open the lock.  In this case, if  11-cis-retinal is isomerized by light, it will not longer fit in properly in the enzyme cavity and will be rejected from the site causing a signal to be sent to the vision center of the brain.

I-E-2.  As can be observed, the values recorded in the table are within experimental error, the same.  However, about 90% of the population can distinguish between the two isomers using odor differeences and the carvones rotate the plane of polarized light in equal magnitudes but opposite directions.

I-F-1.

Compound	oral LD50 value for rats  (mg/kg)	extrapolated amount for 70 kg human (g)
acetaminophen	1944	136
dioxin	0.02	0.0014
vanillin	1580	111

I-F-2.  111 g or about 4 oz is much more than the approximately 5 g of vanillin in a whole cake.  This affords a large margin of safety.

I-F-3.  136/0.5  =  2.7x10² pills

I-F-4.  1.4 mg of dioxin can be toxic but paper products have about 100 ppt (parts per trillion) and weigh about 8 grams.  This means the average plate has about 8x10^-10 grams of dioxin or about 1 millionth of the amount toxic amount.

 

I-F-5.  See:  https://en.wikipedia.org/wiki/Pathophysiology_of_spider_bites 

https://pubmed.ncbi.nlm.nih.gov/3775789/ 

https://untamedscience.com/blog/worlds-deadliest-snakes/  

https://biochem-molbio.imedpub.com/determination-of-lethal-dose-ld50of-venom-of-four-different-poisonoussnakes-found-in-pakistan.php?aid=21045

1.4x10^-4 mL or 0.14 mg could be lethal for spiders and 3.5x10^-2 mL or 35 mg for snakes.  For snakes the average amount of venom injected covers a huge range with 50 mg about average whereas a black widow injects about 3x10^-5 mL or about 0.03 mg.  This calculation assumes humans have the same sensitivity as rats. Also, there is a huge margin of error in all of the measurements involved.  The 0.03 mg injected by spiders is dangerous but not enough to kill most people.  However, 50 mg of snake venom is approximately the LD50 for snakes and could result in death for about half the bites.

II.   Identification of substances from properties.

#	m.p. (oC)	b.p. (oC)	refractive index	IR info	Possible Cmpds.	Suggestions
1		115	1.4100	-OH, -CH3	3-methyl-2-butanol, 3-pentanol, 2-pentanol	nmr
2	122			-OH, C=O	benzoic acid
3		154	1.5160	arom., -CH3	anisole, allylbenzene	ir or nmr
4		202	1.5325	C=O, -CH3	acetophenone
5	81			arom., -CH3	1,2,4,5-tetramethylbenzene
6		78	1.373	-CH3, C=O	methyl propionate, ethyl acetate	nmr
7	114			arom., C=O, -NH, -CH3	acetanilide
8		134	1.4585	sp3 C-H	cyclohexylamine

For more exercises with many spectra included, please visit:

http://murov.info/orglab/51-x5.pdf

http://www3.nd.edu/~smithgrp/structure/workbook.html

https://www.orgchemboulder.com/Spectroscopy/Problems/index.shtml

https://webspectra.chem.ucla.edu//

http://chemistry.miamioh.edu/organicspecid/

http://alpha.lasalle.edu/~price/202 COMBINED SPECTROSCOPY PROBLEMS.pdf 

 

 

 

 

Note 1.  During the preparation of this site, three interesting topics were encountered that did not seem to have adequate discussion during a limited Internet search.

1.  Textbooks claim that except for hydrogen, isotopes have very similar properties but a comparison of physical and chemical properties of isotopes could not be located.  Rate effects and nuclear effects are well documented but melting points and other physical properties of isotopes could not be found (e.g., U-235 and U-238).

2.  The drug Austedo is used for the treatment of Huntington's disease.  It contains deuterium atoms that apparently improve its efficacy.  Although deuterium is an isotope of hydrogen, its properties are different enough that it could be considered to be a separate element but the best definitions of elements include the statement that elements have the same number of protons.  This is a little like the demotion of Pluto from planet to dwarf planet. 

3.  Should there be a correlation between toxicity and color (visible region)? 

4.  A new discovery of a very strong plastic shows that the field of material science is still in its early stages and has extensive potential  https://www.nature.com/articles/s41586-021-04296-3 ,
http://www.sci-news.com/othersciences/materials/2dpa-1-polymer-10518.html

 

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