Chemistry Beyond the Book: - PowerPoint Presentation

Slide1

Chemistry Beyond the Book:Oxygen, Water, Penicillin, Carbon Dioxide, Rust and More orOdds and ends of chemistry that should provide insight into chemistry. Intriguing ideas including the iso words (isotopes, isomers)

Slide2

On this and the previous slide, two very famous chemists are pictured. Who were they?

Marie Curie, Linus Pauling

With regard to the Nobel Prizes,

what did they have in common?

Each won two Nobel prizes.

Marie Curie was the first woman to win a Nobel prize and the first person to win two Nobel prizes. Linus Pauling has been the only person to win two unshared Nobel prizes.

What fields were Pauling’s prizes in?

Pauling won the chemistry and

peace Nobel prizes.

Slide3

As of 9/17, 175 Nobel prizes in chemistry have been awarded. However only 4 women have won chemistry Nobel prizes and a total of 17 women have won Nobel prizes (about 3% of the total awards) . Marie Curie, Irene Joliet-Curie, Dorothy Crowfoot Hodgkin and Ada E. Yonath have been awarded Nobel prizes in chemistry. Chemical and Engineering News on 9/11/17 listed 13 women who did Nobel quality work but for various reasons were not awarded Nobel prizes.http://cen.acs.org/articles/95/i36/female-scientists-should-won-Nobel.html

Slide4

Most basic chemistry courses contain an introduction to measurement tools including units and the metric system, significant figures and rounding off. While these concepts are considered by many to be very dry and of questionable importance, all three play a very valuable role in the interpretation of results and the development of explanations. The next few events are true descriptions of events that resulted from misuse of units.

Slide5

The story of Air Canada Flight 143 (made into a movie as Flight 171) from Montreal to Edmonton on July 23,1983, affords an interesting and relevant example of the importance of unit conversions (P. Banks, Chem. Matters, Oct. 1996, 12-15). A ground crew determined that the flight would require 22,300 kg of fuel and the tanks contained 7,682 liters. To calculate how many liters of fuel needed to be added, they used a conversion factor of 1.77 and assumed the units were kg/L. Unfortunately the conversion factor 1.77 has units of lbs/L. From 1.77 lbs/L, calculate the conversion factor in kg/L. a. 3.90 kg/L b. 1.24 kg/L c. 0.803 kg/L d. none

Slide6

Calculate the volumes in liters needed respectively using the incorrect 1.77 kg/L and the correct value. a. 4.92x103 L, 2.01x104 L b. 1.54x104 L, 1.30x104 L c. none Calculate the shortage in liters of fuel that resulted from the use of 1.77 kg/L instead of the correct value. a. More fuel than needed b. 1.52x104 L c. 9.70x103 L d. none Incidentally, thanks to the heroic work of the flight crew and the air controllers, the flight made a safe emergency landing on an abandoned air strip near Winnipeg considerably short of its destination. In this case a tragedy was averted by both a careful response to the problem and luck. However, proper use of conversion factors with appropriate units coupled with some thinking would have prevented the need for the heroics and a chance for tragedy.Every time a possible solution to a problem is attained, you should ask if the conversion factors used and the answer make sense. The ground crew assumed the density of the fuel to be 1.77 kg/L. Consider the density of water (0.998 g/mL @ 20oC) and of fuel. Are fuels such as gasoline more or less dense than water (< 1 g/mL)? The factor 1.77 kg/L doesn’t make sense and the ground crew should have caught their own mistake and not loaded the plane with the amount of fuel based on 1.77 kg/L.

Slide7

https://www.visionlearning.com/en/library/Math-in-Science/62/Unit-Conversion/144http://articles.latimes.com/1999/oct/01/news/mn-17288 https://en.wikipedia.org/wiki/Mars_Climate_Orbiter Mars climate orbiter

Slide8

Hubble telescope mistakehttp://www.spacetelescope.org/about/history/aberration_problem/ https://spaceflightnow.com/2015/04/23/fixing-hubbles-blurry-vision/https://www.newscientist.com/article/mg12717301-000-the-testing-error-that-led-to-hubble-mirror-fiasco/ For more examples of calculation errors, see: http://www.bbc.com/news/magazine-27509559

Slide9

List several reasons the metric system is superior to the American customary system.Metric American Customary systemUnits related by powers of 10 units related by random factors – 2, 3, 12, 16, 36, 5280, etc.Volume related easily to cube of distance complex relationship between vol. and dist.3Volume and mass of water easily related a pint is a pound of water is off by 4%Metric system used in most countries requires a second set of toolsLogical abbreviations some abbreviations illogical (lb., oz..)0oC and 100oC, 100 divisions 32oF and 212oF, 180 divisionsDoesn’t need mixed units Often mixes units (5 ft, 8 inches tall)

Slide10

Slide11

A “vertical” periodic table is shown in the figure to the right. Suggest a couple of advantages of the vertical table compared to the traditional (“horizontal”) table. On a normal 8.5 x 11 inch piece of paper, the chart does not have to be rotated 90o to easily read it. Unfortunately, the vertical model does not fit as well as the horizontial on this slide. More importantly, since we read left to right, the vertical model puts more focus on groups compared to the focus on periods in the traditional model.

Slide12

Some chemistry problems that should be easy are challenging to many students. For more chemistry problems, see: http://exercises.murov.info/chemexercises.htm (basic chemistry)http://murov.info/orglab/47-x1.pdf (general chemistry)http://murov.info/orglab/exercises.htm (organic chemistry)What is the mass of one atom of carbon? A 75 gram sample of an unknown element is found to contain 0.50 moles. What is the element? 3 What are the quantum numbers (n, l) for a 3 p electron? An electron with quantum numbers 4, 2, 1, ½ should be represented by what symbolism (see # 3)? 5. What is the molarity to two significant figures of water at 20oC? 6. Assume that you have 1.00 L of water that has very recently been distilled and has pH = 7. What will the pH be if you add 1 drop (0.050 mL) of 1.0 M HCl to the water? 1.99x10

-23 gSince the molecular mass is 150 g/mol, probably Sm

3, 14dmol/L4.3

Slide13

What is the limiting reagent in this reaction?bI2See d above, O2 in excessCOCl2 = CO + Cl2

Slide14

The  must break as well as the Cl-Cl bond. Two new carbon – chlorine bonds form.

Slide15

O2 + 2 NO = 2 NO22 CH4O + 3 O2 = 2 CO2 + 4 H2ON2H4 + O2

= N2 + 2 H2O

Slide16

Name the elements that occur in elemental form on earth.

http://murov.info/pertab-eleform.pdf

The inert gases are also called the noble gases. The metals ruthenium (Ru), rhodium (Rh), palladium (Pd), silver (Ag), osmium (Os), iridium (Ir), platinum (Pt), and gold (Au) are sometimes called the noble metals. Why?.Like the noble gases, the noble metals are rather unreactive.

Slide17

The graph below shows the number of isotopes as a function of atomic number. Which statement below the graph is true? Click on the answer you think is correct.Multiple isotopes often exist for nuclei with an even number of neutrons.Multiple isotopes often exist for nuclei with an even number of protons.Odd atomic numbers usually have multiple isotopes.None of the above.b.

Slide18

The value of the atomic mass provides more information than most students realize. The following questions strive to demonstrate the potential uses of atomic mass. Point and click on correct answer.According to the periodic table, how many protons,electrons and neutrons (on average) does an atomof fluorine (at. # = 9, mass = 18.998) have?9, 9, 9 b. 10, 9, 9 c. 9, 10, 10 d. 9, 9, 10 e. NoneHow many neutrons does an atom (at. # = 79) of gold (mass = 196.97) have?a. 197 b. 79 c. 118 d. An average of 118 e. NoneThe atomic mass of gold of 196.97 indicates:a. There is probably a preponderance of only 1 isotope of gold.There are probably many naturally occurring isotopes of gold.None of the above.

Atomic mass values represent the measured value of the mass of

the naturally occurring mixture of the isotopes of the element on earth.A measured value close to unity is most likely because almost all of the atoms of the elementexist in one isotopic form. If 2 or more isotopes are common, only an unusual coincidence wouldresult in an atomic mass close to unity. This does happen (e.g., see bromine).

Slide19

Chlorine has an atomic number of 17 and an atomic mass of 35.457.Point and click on the correct statement below.A chlorine nucleus has 18.5 neutrons.Chlorine has at least two naturally occurring isotopes.About half of chlorine atoms have 18 neutrons and the other half 19 neutrons.None of the above.b. It is not possible to have a partial neutron so “a” is impossible. The atomic mass is the measured value of the atomic mass of chlorine on earth. The value is not near unity so more than one isotope of chlorine must exist. It is not possible to determine from atomic mass alone which isotopes are present. With chlorine, the value of the atomic mass only tells us that some of nuclei have more than 18.5 neutrons and some less. A mass spectrum is needed to determine which isotopes exist and their abundance. The mass spectrum to the right shows that there is about 3 times as much chlorine-35 as chlorine-37. Chlorine-36 is unstable and is not found in nature.

Slide20

Slide21

Only some combinations of protons and neutrons are stable. For the first twenty elements, the number of protons and neutrons are similar. After calcium, on average, more than one neutron is added for each additional proton (supposedly to keep the positively charged protons separated). A previous slide gave the number of isotopes that are found in nature as a function of the atomic number. If an isotope is not found in nature, there is a very high probability that the combination of protons and neutrons result in an unstable nucleus. When a combination is unstable, the nucleus decays with a half life that can range from a fraction of a second to billions of years. It is difficult to predict which combinations should be stable but an earlier question demonstrated that elements with an even number of protons tend to have multiple stable isotopes whereas elements with an odd number of protons frequently have only one stable combination. Some information about the stability of isotopes can be obtained using the atomic mass from a periodic table. If a proposed isotope has a number of neutrons close to the value calculated from the atomic mass, there is a chance the isotope is stable. The greater the deviation of the number of neutrons from the calculated number, the greater the chance that the nucleus will be radioactive with the caveat that the higher the mass, the greater a stable deviation is possible. Use a periodic table to suggest which of the following nuclei should be stable.hydrogen–2 hydrogen-3 carbon-12 carbon-13 carbon-14strontium-88 strontium-90 uranium-238 uranium-235

Slide22

Carbon has an atomic mass of 12.011 again indicating the existence of primarily one isotope. However, since carbon-12 has been assigned a mass of exactly 12, the value of 12.011 indicates a heavier stable isotope must exist in nature. Stable carbon -13 is about 1% of the carbon in nature and differs from the periodic table value by only 1. Carbon-14 undergoes  decay with a half life with a half life of 5730 years and differs by 2 neutrons from the periodic table value.Hydrogen has an atomic mass very close to unity (1.008) indicating almost all hydrogen atoms have no neutrons. 0.015% of hydrogen atoms have 1 neutron. It is not surprising that hydrogen-2 (called deuterium) is stable as it differs from the periodic table prediction by only 1 neutron. However, hydrogen-3 (tritium) differs by 2 neutrons and decays by  decay with a half life of 12.3 years.

Slide23

Strontium has atomic # of 38 and an atomic mass of 87.62. The significant deviation from unity correctly indicates that there is more than one naturally occurring isotope of Sr. Since Sr has an even # of protons, it is not surprising that there are multiple (4) stable isotopes. However, it should be suspected that strontium-90 could be unstable as it differs by more than 2 neutrons from the value in the periodic table. Strontium-90 undergoes  decay with a half life of 29.1 years and is a common component of radioactive fall out.

Slide24

Uranium has atomic # 92 and an atomic mass of 238.03. There are no completely stable isotopes after the element bismuth (technically, even bismuth-209 is very slightly radioactive with a half life over 1019 years). However, the half live of uranium-238 is about the age of the earth (4.5x109 years) meaning that about half of the uranium that was formed when the earth was formed is still here. Uranium-235 has a half life about 15% as long as uranium-238. As indicated by the atomic mass and consistent with the half lives, 99.3% of the uranium on earth has a mass of 238.05 and most of the remaining 0.7% is uranium-235. The proportion of uranium-235 has been decreasing on earth since its formation. Uranium-235 is capable of undergoing fission and is used in nuclear energy facilities and atomic bombs. Uranium-238 does not fission. This means that uranium-235 must be concentrated from uranium ore via a very expensive separation process.

Slide25

https://blogs.scientificamerican.com/guest-blog/natures-nuclear-reactors-the-2-billion-year-old-natural-fission-reactors-in-gabon-western-africa/ https://www.scientificamerican.com/article/ancient-nuclear-reactor/ https://en.wikipedia.org/wiki/Natural_nuclear_fission_reactor For information on a natural nuclear reaction, see:

Slide26

Many common explosives contain nitrogen.

Suggest explanations for this observation.When compounds containing nitrogen decompose, very stable nitrogen gas is released. Because of the nitrogen stability, the decomposition is hugely exothermic and also includes the production of a very high volume of hot gas.

Slide27

Lewis structures, oxidation numbers and formal charges normally are consistent with basic principles. However, deviations from “normality” should be carefully noted and are often a good predictor of unusual behavior.With Lewis structures, failure to be able to achieve an octet (for the first 3 periods - beyond the 3rd period, octets are often exceeded due to the presence of d orbitals) is usually a strong indicator of high reactivity. For example, the Lewis structures of nitrogen monoxide and nitrogen dioxide each have an unpaired electron in the structure. Free radicals are notoriously reactive as reaction usually results in the pairing of all electrons. Draw the Lewis structures of F, F2 , NO and NO2. The free radicals F, NO and NO2 are all very reactive with fluorine atoms dimerizing to make diatomic fluorine, NO reacts quickly with oxygen to give NO2 and NO2 partially dimerizing to give N2O4.

Slide28

Draw the Lewis structures of an oxygen atom and diatomic oxygen following the basic rules for the drawing of Lewis structures.The Lewis structure of O2 shown above has been drawn according to the guidelines for drawing Lewis structures. However, when liquid oxygen is poured between the poles of a magnet, the left deflection (to the right) is clearly observed. This observation demonstrates that the Lewis structure model above is not correct as the deflection toward one pole is strong evidence that diatomic oxygen has at least one unpaired electron. O2

is one of the very few cases where the basic Lewis structure does not model the correct properties. The Lewis structure to the right does correctly predict paramagnetism but violates the octet rule and does not show the double bond. Molecular orbital theory, unlike the Lewis structure above, does give a good model of O2 with 2 unpaired electrons.

Slide29

There are three allotropes of oxygen; O, O2 and O3. O2 occupies 21% of our atmosphere and not surprisingly due to its diradical character is reactive. Rusting and combustion are two commonly observed reactions of diatomic oxygen. Due to the favorable dimerization (O + O = O2) reaction of oxygen atoms, oxygen atoms are seldom encountered. O3 or ozone is much more reactive than O2 making it very toxic to humans. Ozone is a vital component of the upper atmosphere as it absorbs damaging UV rays. Unfortunately, ozone is a significant toxic component of smog. Use the Lewis structures of ozone to determine the formal charges of the oxygens in ozone. Do the formal charges give any clues concerning the reactivity of ozone. The exterior oxygens of ozone each have a formal charge of -0.5 and the middle oxygen has a formal charge of +1. The +1 formal charge contradicts expectations for very electronegative oxygen and provides an indication that the molecule will react to eliminate the positive formal charge.

Slide30

In the early 1970’s, two UCIrvine scientists, Rowland and Molina, based on primitive data, calculated that continued use of freons as refrigerants and propellants would cause a dangerous depletion of the ozone layer. One consequence would be a corresponding increase in skin cancer. As the years passed, refinement of the data and atmospheric measurements supported the conclusions of Rowland and Molina. Both were awarded Nobel prizes and their research enabled the drafting and passing of the Montreal Protocol in 1989 that has phased out the use of the most hazardous of the freons. An ozone hole that developed annually over the Antarctic has peaked in size in 2006 and seems to be slowly returning to pre-freon size.

Slide31

Permanganate, chromate, chlorate, perchlorate and nitrate all can be used as oxidizing agents. Suggest a reason for this mode of reactivity.For each of the polyatomic ions mentioned, the central atom has a calculated oxidation number (large and positive that leads to high reactivity).Laughing gas (N2O) has a Lewis structure that contradicts the common observation that polyatomic species have a symmetrical distribution of the atoms. Based on Lewis structures for NNO and NON, explain why the assymetrical structure better corresponds to other Lewis structure guidelines.The resonance structures of NNO do have formal charges but the resonance structures of NON have even more unfavorable formal charges and/or lack octets.

Slide32

Determine the oxidation state(s) of iron in Fe3O4. The calculation yields a value of +2. A more realistic model has one of the irons with a +2 and the other two irons with a +3 averaging out to 2. Unusual results such as fractional oxidation states often are indicative of unusual behavior. A common name for Fe3O4 is magnetite. As observed in the image, magnetite has the extremely rare property for a compound of being ferrimagnetic (similar to ferromagnetic).The magnetic domains that cause ferromagnetism are regions in which the spins of large numbers of unpaired electrons of neighboring atoms align with each other, creating a unidirectional magnetic field. This alignment of spins arises from an atomic-level quantum mechanical interaction. Ferromagnetism and ferrimagnetism are both forms of magnetism, the familiar force that attracts or repels certain metals and magnetized objects. The differences between the two properties occur at microscopic scales.

Slide33

LiAlH4, NaBH4 and other hydrides are very useful as selective reducing agents in organic chemistry. Determine the oxidation number of hydrogen in these hydrides. Does the oxidation number give any insight regarding the reducing ability of hydrides.The oxidation number of hydrogen in hydrides is -1. It is generally energetically favorable for a hydride to react.Methylene (or carbene) has the formula CH2 and is highly reactive. Why is methylene so reactive?

In the electronic structure of methylene, the carbon is 2 electrons short of an octet resulting in high reactivity.For Donald Duck cartoon on methylene, see:https://www.uky.edu/Projects/Chemcomics/html/dd_15_2_n.html

Slide34

It is possible to draw two Lewis structures for carbon monoxide. Both have issues with Lewis structure guidelines. What are the issues? Do these issues account for any of the properties of CO?In one of the Lewis structures, the carbon has a -1 formal charge and the oxygen has a +1 formal charge. Generally, an attempt is made when drawing Lewis structures to minimize formal charges (in this case the opposite of expectations from electronegativities) but this leads to the 2nd structure. The formal charges are in line with expectations but the carbon atom lacks an octet. The issues for both raise flags that should be recognized as an indication of unusual behavior. Experimentally, the C-O bond length indicates a triple bond is present. Breathing of CO can be fatal as the CO bonds to iron even better than even reactive oxygen does.

Slide35

Draw a Lewis structure for water. What bond angle for the H-O-H structure is predicted by the Lewis structure?The model indicates that the oxygen is sp3 hybridized since it has 2 bonds and 2 non-bonded pairs of electrons. sp3 orbitals are oriented in a tetrahedral configuration with 109.47o bond angles. The actual bond angles in water are 104.45o sometimes attributed to enhanced repulsion between the non-bonded pairs that forces the hydrogens closer together. Another approach is to consider the oxygen to be un-hybridized. For this model, the bond angle would be 90o. Why? Another explanation for the actual value could be that the oxygen is only partially hybridized.

= 9.6x10-11 m

= 3.8x10-9 inches= teeny, tiny!!

Slide36

Because of the electronegativity difference between O and H, the O-H bonds are significantly polarized with a partial negative charge on the O and partial positive charge on each hydrogen. Due to the bent structure, the bond polarities result in a large net dipole for the molecule. What is the most important consequence of the bent structure compared to a linear structure?A linear structure while having polar bonds would have zero net polarity. Therefore, ionic compounds such as salt would likely have low solubility in water. Because of the polarity that results from the polar bonds and the bent structure, water is a very good solvent for polar molecules.

Slide37

Based on polarity considerations, should iodine be very soluble in water?Although the substantial amber color might lead to the conclusion that iodine is soluble in water, polarity considerations (water is polar and iodine non-polar) lead to the correct conclusion that iodine has a low solubility in water (0.03%). Iodine has a very good ability to absorb light (high extinction coefficient) resulting in a colored solution with very little iodine. The iodide raises the solubility of iodine by reacting with iodine to form polar triiodide. The color of most compounds is relatively insensitive to the nature of the solvent. However, the color of iodine solutions in non-polar organic solvents is rather different than the color in water. The test tube contains water and cyclohexane.

Slide38

Another consequence of the polar bonds in water is the ability of water to form hydrogen bonds to itself and F, O, or N atoms in another molecule. Hydrogen bonds are only possible when a hydrogen is bonded to F, O, or N and then can only form hydrogen bonds to the same 3 elements. Name some of the important roles that hydrogen bonding plays in nature.Due to H bonds, the boiling point of water is over 100o higher than would be predicted in the absence of H bonds. Compounds capable of H bonding generally have higher boiling points than would be expected. A solute that is capable of H bonding will generally have enhanced solubility in a solvent that is capable of H bonding. H bonding plays an extremely important role in determining the structure of DNA, RNA and proteins as well as the DNA coding.

Slide39

The two beakers and test tubes below each contain only one substance. Which substance exhibits abnormal behavior?

Acetophenone Water

Because water is probably the only substance for which you ever see both the liquid and solid phases in the same system, you have probably accepted the observation of its behavior (solid floats in the liquid) as normal. However, if you think about it, the solid should be more dense than the liquid and sink. Almost all substances other than water behave like

acetophenone so water behaves abnormally. Why does water have an anomalous solid-liquid density relationship?

acetophenone water acetic acid

dioxane

p

-xylene oleic acid

Slide40

This slide shows that H

2

O molecules form an organized structure in ice (figures on right) that results in more space and a lower density than in liquid water (figures on left). For Calvin and Hobbes cartoon on floating ice, see:http://www.s-anand.net/blog/calvin-and-hobbes-dad-explains-science/

Slide41

Chemists use the mole as a basic unit.One mole is the number of atoms of carbon in 12 g (0.42 oz.) of carbon or602,000,000,000,000,000,000,000 atoms(6.02x1023 atoms). Would a mole of marshmallows cover the 48 contiguous states of the U.S. ?

Slide42

Your first response should be – whatsize marshmallows? Assumingregular size marshmallows, a mole of marshmallows would cover the United States to a depth of about 600 miles.

When you drink a glass of water, you swallow

about 10 moles of water or 6 septillion (6x1024)6,000,000,000,000,000,000,000,000molecules of water. It has been reported thatthe Universe has about 1/2 of a mole of stars.

= 9.6x10

-11

m

= 3.8x10

-9

inches

= teeny, tiny!!

Slide43

The table below is one of the modern electronegativity scales. The values are similar to but sometimes meaningfully different from the original Pauling electronegativities. http://www.meta-synthesis.com/webbook/36_eneg/electroneg.html The values should be used with caution as some predictions that result from the use of these values are inconsistent with observations. According to the values, chlorine is more electronegative than nitrogen. Which of the two elements forms H bonds and is this consistent with the values?Sulfur and Iodine when bonded to sp3 carbons are susceptible to attack by nucleophiles with displacement of the S or I and substitution by the nucleophile. Are these nucleophilic substitution reactions consistent with the bond polarities predicted for C-S and C-I bonds?a. Hydrogen bonds are observed with N but not Cl. This is contradictory to the electronegativity values indicating other factors such as atomic size could play an important role in the formation of H bonds.b. The electronegativities of C, S and I are all within experimental error of each other indicating non-polar bonds. Nevertheless, the C-S and C-I bonds behave like they are polar bonds with a partial positive charge on the carbon.

Slide44

The boiling points of several binary compounds containing hydrogen are given in the table below. Explain how the values for ammonia, water and hydrogen fluoride provide evidence for hydrogen bonds but the value for hydrogen chloride indicates an absence of H-bonds.The trend going up Group IV is fairly consistent but the values for ammonia and water are much higher than predicted by the trends going up Groups V and VI. The value for HCl is consistent with the trend set by HI and HBr but is actually much lower than should be expected going across its period. Some argue that HF is lower than water because water has more H bonds possible per molecule than HF but this argument has a problem when ammonia is considered.

Slide45

One of the octane systems of rating appropriate gasoline combustion rates is based on setting values of 100 for isooctane and zero for normal heptane. According to the convention for naming organic compounds, iso means there is a methyl branch on the next to last carbon which means that isooctane should be 2-methylheptane. Unfortunately, the name isooctane has been used to represent 2,2,4-trimethylpentane. What is the relationship between 2-methylheptane and 2,2,4-trimethylpentane.Compounds that have the same formula (C8H18) but differ in structure in any way are called isomers. 2-Methylheptane and 2,2,4-trimethylpentane are structural isomers and have different properties.

heptane

2-methylheptane

Slide46

Ammonium cyanate and urea have the same formula but different structures and properties. AgOCN + NH4Cl = NH4OCN = AgClNH4OCN(aq)  CO(NH2)2(aq)Frederich Wöhler was given credit for redefining organic chemistry when he debunked the concept of vitalism (organic compounds are derived from once living species and have a special attribute called vitalism) in 1828 by converting a compound considered to be inorganic (ammonium cyanate) into one derived from living species (urea). His demonstration also was one of the first demonstrations of the concept of isomerism. Explain how his experiment relates to isomerism.Wöhler is also famous for his comment on organic chemistry - Organic chemistry nowadays almost drives me mad. It gives me the impression of a primeval tropical forest, full of the most remarkable things, a monstrous and boundless thicket, a dreadful, endless jungle with no way of escape, into which one may well dread to enter for there seems no way out.Author’s comment: During the last couple of centuries, great strides have been made towards unraveling the mysteries of organic chemistry. While still “full of the most remarkable things,” organic chemistry has been developed into a comprehensible and fascinating science.

Slide47

Besides structural isomers (compounds with the same formula that differ in the sequence of bonding), other types of isomers include stereoisomers. Stereoisomers have the same sequence of bonding but differ in the position of the atoms in 3D. Geometric isomers are one type of stereoisomer as will be illustrated below for C

2

H2Cl2. Draw the structures of the geometric isomers of dichloroethylene as well as a structural isomer of the 2 geometric isomers. Notice after the answer appears that some of the physical properties of the 3 isomers are different.

Slide48

Geometric isomerism is extremely important and in fact is responsible for the first step in vision that is enabling you to read this page. The absorption of light by cis-retinal causes an isomerization to trans-retinal. This geometric change triggers a signal that is sent to your brain that enables vision.

Slide49

An even more intriguing type or stereoisomerism is possible when a compound has a tetrahedral carbon with 4 different groups attached as illustrated below for a generic  amino acid. While an initial inspection might lead to the conclusion that the two molecules are identical, use of molecular models reveals that the two structures are non-superimposable mirror images. It does not matter how you turn or orient the structure on the right, the position of the groups attached to the carbon will not coincide with the structure on the left. Experimentally, what are the observable results that are typical of mirror images?There are two major differences between non-superimposable mirror images. Plane polarized light is rotated in opposite directions by enantiomers. See the next slide for the even more important effect.

Slide50

Enantiomers interact with other enantiomers in different ways. As shown in the following image, the R enantiomer fits like a key into a lock in the receptor site (perhaps an enzyme) but the S enantiomer does not fit the lock.One easily observed example involves carvone. The R isomer can be isolated from oil of spearmint while oil of caraway yields the S isomer. Most people can distinguish the two by odor. The conclusion is that the two compounds behave differently in the presence of nasal receptors. The medical differences are demonstrated by thalidomide and ibuprofen.

Slide51

sleep inducing teratogenic

ibuprofen

Slide52

Many natural products including amino acids and carbohydrates contain one or more carbons (chiral carbons) that have four different groups attached to them. 6 carbon sugars (hexoses) have several chiral centers leading to many stereoisomers. Essentially all amino acids found on earth have the L configuration and the sugars have the D configuration. A diet consisting of the D amino acids or the L sugars would result in death as earth based animals only have the enzymes needed for metabolizing the L amino acids and the D sugars.

Slide53

If you cannot answer the question below correctly, you should learnmore about climate change before you accept or reject the conclusionsof 97% of the climate scientists that humans are a major contributor to global warming. What are the three most abundant gases in dry (not counting water) air?

Answer on the next slide -

Slide54

The table above reveals that carbon dioxide is a distant 4th at 0.04% and rising. How does this value relate to the science of global climate change? See next slide.

Slide55

As shown in the two figures, CO2 was relatively flat at 280 ppm until the industrial revolution and the extensive burning of fossil fuels began. CO2 increases the amount of IR radiation emitted by the earth that is absorbed. As a result, the earth is warming. A 2nd dangerous effect is that some of the CO2 is absorbed by the oceans resulting in a pH decrease. This poses a severe threat to shell fish.

Slide56

H

2

O + CO2 = H2CO3 For Calvin and Hobbes cartoon on the Greenhouse effect, see:http://3e.org/feeds/ch/87/8707.htm

Slide57

codeine methadone dextromethorphan

heroin morphine

vicadin

demerol

The structures of some opioid related drugs are shown below. Notice the structural similarities

and differences.

Dextromethorphan is commonly included in over the counter cough medicine.

Slide58

j

-NH2

Penicillin GThe first penicillin (G) was discovered serendipitously by Fleming in 1928 but methods of delivering it were not developed until WWII. Unfortunately, G does not survive stomach acid and must be injected. Ampicillin and amoxicillin were developed and can be taken orally. Suggest a reason for the stability of these penicillins in the stomach.AmpicillinBoth ampicillin and amoxicillin have an NH2 that is protonated by stomach acid and forms an ion that is stable in the stomach.

Slide59

Serendipitous DiscoveriesWhat does serendipitous mean?Penicillin TeflonSaccharinCyclmateAspartame

i

Sucralose

occurring or discovered by chance in a beneficial way (but preparation really helps)

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Wallace Hume Carothers (1896––1937) discovered nylon in 1934

http://www.chemheritage.org/EducationalSe

rvices/chemach/pop/whc.html Explain what the 3 sequential arrows in the equation below represent.

The diacid chloride and the diamine each have 2 reactive ends. After a molecule of each reacts to give an amide, the remaining ends of the molecule can react with another molecule of diamine and another diacid chloride and this process can go on hundreds of times. The result is a polymer called nylon 66.

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http://www.chm.bris.ac.uk/sillymolecules/sillymols.htm

http://en.wikipedia.org/wiki/List_of_chemical_compounds_with_unusual_names

http://io9.com/5863943/10-bizarre-names-and-strange-origins-of-real-molecules

http://chemistry.about.com/od/chemistryfunhumor/Chemistry_Fun_Humor.htmSome molecules with interesting names.cubane

prismanebarrelene

buckministerfullerene

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Selected organic molecules have extra stability that can be attributed to a special type of resonance called aromaticity. Aromaticity generally occurs in planar conjugated cyclic systems with 4n + 2  electrons. Benzene is the most famous of the aromatic molecules but there are many more.The planar form of cyclooctatetraene would have bond angle strain but because the planar form would not be aromatic (4n electrons), the molecule bends and the  bonds are not conjugated. Cyclobutadiene is not exactly flat.benzene

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