1. Give the best answer for the following multiple choice and labeling questions.
a) Which of the following will not react with a grignard reagent?
b) The addition of a grignard reagent to a carbonyl is based on collision of a nucleophile to fill what acceptor orbital?
A) a s bonding orbital
B) a s* antibonding orbital
C) an empty p orbital
D) a p bonding orbital
E) a p* antibonding orbital
c) Which reactions will not give a product as a racemic mixture?
A) the addition of phenyl grignard to propionaldehyde
B) epoxidation of an allylic alcohol with a Ti(OiPr)4, tBuOOH, and (–)-diethyl tartrate
C) the addition of NaOCH3 to cyclohexene oxide
D) the acid-catalyzed addition of methanol to cyclohexene oxide
E) an SN1 reaction
d) Which of the following is not a true statement:
A) a silyl ether bond can be cleaved by a fluoride source, such as TBAF
B) LiAlH4 is an oxidizing agent
C) epoxide formation using mCPBA with an alkene proceeds via a concerted mechanism
D) H2CrO4 will oxidize a secondary alcohol to a ketone
E) arene oxides can react with DNA and initiate cancer-causing pathways
e) In the boxes provided, indicate whether each of the following reactive carbon atoms is considered to be electrophilic (E) or nucleophilic (N). R is used to indicate either H or alkyl.
2. Draw the resonance contributor for a ketone, showing any curved arrows for its formation. Briefly explain what this resonance indicates about the reactivity of a carbonyl.
3. Ethylene oxide is the starting material for the synthesis of “Cellosolve”, an important industrial solvent. Provide a curved arrow mechanism for this reaction.
4. Provide a curved arrow mechanism for the following transformation.
a) Show how to synthesize the following alcohol where all carbons in the molecule must come from compounds with 3 or fewer carbon atoms. Include all necessary reagents for the synthesis you propose.
b) Explain why you would need to use a protecting group strategy in a synthesis and give an example of a synthesis that requires the use of a protecting group. Your synthesis must have at least 3 steps to receive full credit.
6. An aziridinium ion follows a similar reactivity pattern to an epoxide. The following aziridinium ion reacts with NaOCH3 to form compounds A and B. Given what you know about the reactivity patterns of epoxides and the information given below, identify the structures of both compounds A and B (in boxes provided).