ORGANIC CHEMISTRY II QUIZ KEY (20 points)

1. ORGANIC CHEMISTRY IIQUIZ KEY(20 points)

2. 1. (5 points) “Describe in detail” why the molecule benzene has resonance and what is the significance of this resonance in the ring structure. Use significant and substantial sentences and not phrases. "USE ALL APPROPRIATE TERMINOLOGY NECESSARY"

3. Benzene exhibits resonance because its three double bonds are delocalized between all six carbon atoms in the ring, instead of stationary double bonds between just two carbon atoms. The hybridization for the entire benzene molecule, therefore, takes on sp2 hybrid orbitals for the carbon atoms instead of sp3 hybrid orbitals. Each carbon-carbon bond still has one sigma bond in addition to its pi bond that extends above and below the flat plane of the sigma bond. The bond lengths and bond strengths of one and a half (1 ½) are shared between the six carbons, making the benzene molecule unusually stable and unreactive like an alkane. One common symbol for benzene, a hexagon with a circle in the middle, illustrates the shared sp2 hybrid orbitals and the resonance of the benzene ring.

4. 2. (8 total points) a. (2 points) “Explain in detail” why there is only one "monsubstituted product" of benzene. b. (6 points) Name the three "disubstituted products“ of benzene and explain how and why they are different from each other in a positional sense. Use sentences and not phrases as noted above. "USE ALL APPROPRIATE TERMINOLOGY NECESSARY"

5. a. Benzene is a symmetrical, 6-carbon molecule. If only one substituent group is attached to the benzene it doesn't matter where it is located because there are no other groups in relation to it and it can be precisely reproduced experimentally given just an IUPAC name. b. The "o" or "ortho" location is "one-carbon-away" from the attachment the molecule is named for. The "m" or "meta" location is "two-carbons-away" from the substituent group the benzene molecule is named for. The "p" or "para" location is "three-carbons-away" from the substituent group the benzene molecule is named for. In the case of ortho groups and meta groups, the substituent molecules can be either clockwise or counterclockwise from the group the molecule is named for. In the case of a para attachment, however, there is only one position exactly across the benzene from the group the molecule is named for.

6. 3. (7 points) “DESCRIBE” the general structures of the following functional groups including what makes them unique. What are their similarities and differences. a. Carboxylic acid: b. Salt of a carboxylic acid: c. Ester: d. Amide: e. Aldehyde: f. Ketone: g. Acid chloride "USE ALL APPROPRIATE TERMINOLOGY NECESSARY"

7. a. A carboxylic acid has a carbon (with an OH group attached and double-bonded with another oxygen and hydrogen) attached to an R group. It has the characteristic formula, R-COOH. Carboxylic acids have the suffix -oic acid. b. The salt of a carboxylic acid is similar to a carboxylic acid, except that one of its oxygens is is bonded to a metal cation. It takes this form: the C attached to the R group is double-bonded to an oxygen and to another oxygen that is bonded to the metal cation. It has the characteristic form R-COO-(metal cation)+. The oxygen exhibits a negative charge creating a bond with the positive metal cation. Salts of carboxylic acids end with the suffix -oate. c. An ester is also grouped as a carboxylic. Attached to the R group there is a carbon double-bonded to oxygen as well as another oxygen with is, in turn, bonded to another R group. The characteristic formula is R-COO-R. Esters have the suffix -oate. d. Amides are carbonyls. Attached to the R group there is a carbon double-bonded to an oyxgen and also bonded to an NH2 (the amide). The resulting form is R-CONH2. The suffix of amides is -amide. e. Aldehydes are carbonyls. Attached to the R group there is a carbon (with a hydrogen on it) double-bonded to an oxygen. Aldehydes are always on the ends of molecules. The suffix of aldehydes is -al. f. Ketones are carbonyls. They are very similar to aldehydes, except they between R groups in the middle of molecules. The carbon, double bonded to an oxygen, is in between to R groups in this case. The characteristic formula is R-CO-R. The suffix of ketones is -one. g. Acid chlorides are carbonyls. Attached to the R group is a carbon atom double-bonded to oxygen and also bonded to a chlorine atom. It has the general form R-COCl. The suffix of acid chorides is -oyl chloride.

8. 4. (5 points) “Explain” how and why carboxylic acids and their derivatives display resonance and what makes this so important in these structures. "USE ALL APPROPRIATE TERMINOLOGY NECESSARY"

9. Carboxylic acids, their salts, esters and amides all display resonance because the pi bond from the carbon double-bonded with oxygen is delocalized with the carbon's other single-bonded oxygen atom(the nitrogen atom for amides). This is the defining characteristic of the carboxyl group. The double bond between the carbon and its oxygen is "spread" to the carbon's other oxygen single bond (again, the nitrogen atom for amides). This gives the carboxyl structure a bond length of one and a half (1 ½) , a bond strength of one and a half (1 ½) and makes the whole structure more stable and somewhat unreactive. The hybridization for these three atoms is sp2!