Final Exam, May 4, 1999
1. (8) Give correct IUPAC names for the following compounds. Include E or Z designations designations where necessary.
2. (8) Draw structures which correspond to the following IUPAC names. Where R or S designations are given, you may answer with either a perspective or a Fischer formula.
|a. meta-nitrotoluene||b. R-3-bromo-1-pentene|
3. (20) Give short answers to the following questions.
a. Write the mRNA sequence which would be produced by transcription of the following DNA segment:
b. Attempts to carry out SN2 reactions on tertiary alkyl halides fail. What happens instead?
c. What structural characteristic is necessary for an atom to behave as a Lewis base?
d. Which nucleophilic substitution reaction involves a carbocation intermediate?
e. Hydrogen bonds are a major factor responsible for the specificity of base pairing in DNA replication, transcription, and translation. Give an example of a hydrogen bond and explain the structural factors which lead to the attractive force.
4. (24) a. Circle a carbon atom which is attacked by a nucleophile. Underline a carbon atom which is attacked by an electrophile.
b. Circle the alkyl chloride which would react most rapidly with iodide ion in an SN2 reaction. Underline the alkyl halide which would react least rapidly.
c. Circle the enantiomer of the structure in the box. Underline the diastereoisomer of the structure in the box.
d. Circle the structure of the compound which reacts fastest with bromine and a FeBr3 catalyst. Underline the structure of the compound which reacts slowest with bromine and a FeBr3 catalyst.
e. Circle the reagent which is used to identify the N-terminus amino acid in a peptide. Underline the reagent which is used to make the peptide (amide) bond in the synthesis of peptides.
f. Circle the structure whose functional group includes an sp2 hybridized carbon. Underline the functional group whose structure includes an sp hybridized carbon.
5 (48) Give the principal organic product(s) of each of the following reactions. If an ortho-para mixture constitutes the largest fraction of the product, give structures for both isomers.
6. (30) For each of the following reactions, write the structure or the formula of the missing reagent, reactant, and/or catalyst in the box. In some cases, a sequence of reagents, etc., may be necessary. In such a case, clearly indicate the order in which the reactions are to be done.
7. (32) Show how you could carry out the following synthetic transformations by listing the necessary reagents in the appropriate sequence. Several steps may be needed in each instance.
8. (16) Propose mechanisms for the following reactions. Be sure that your diagrams clearly show what you want your answer to mean.
9. (14) Answer each of the following questions and explain your reasoning. Illustrate your explanation by including and discussing appropriate structures for significant intermediates, resonance structures and/or transition states.
a. Phenols (pKa ~ 10, the OH group is directly attached to the benzene ring) are more acidic than alcohols (pKa ~ 16). Why?
b. Threose is a D-aldotetrose. When threose is reduced by sodium borohydride an optically active compound (called threitol) is formed. When the Kiliani-Fischer chain extension reaction (an example is given below) is applied to threose, two stereoisomeric D-aldopentoses, A and B, are obtained. A is reduced to an optically inactive compound by sodium borohydride. B is reduced to an optically active compound by sodium borohydride. Give Fischer projection formulas for threose, A and B.
cf 15.18, 19
(An example of the Kiliani-Fischer chain extension)