Question 1

Which of the following substituents on a benzene ring will most increase the acidity (lower the pKa) of a phenol group attached to the ring?

Accepted Answer

A nitro group ($-NO_2$) at the para position

Question 2

In a Wittig reaction between benzaldehyde and methyltriphenylphosphonium ylide, which product is favored and what is its stereochemistry?

Accepted Answer

The E-alkene is favored due to steric hindrance

Question 3

Which of the following carbonyl compounds will have the smallest $K_{eq}$ for hydrate formation in water?

Accepted Answer

Benzaldehyde ($C_6H_5CHO$)

Question 4

What is the major product when 1-bromopropane reacts with sodium ethoxide ($NaOEt$) in ethanol?

Accepted Answer

Propene ($CH_2=CHCH_3$)

Question 5

Which reagent would you use to convert a ketone to a secondary alcohol in one step?

Accepted Answer

$LiAlH_4$, ether, then $H_2O$

Question 6

A student attempts to synthesize 1-phenyl-2-propanol from benzaldehyde using a Grignard reagent. Which Grignard reagent should be used?

Accepted Answer

$CH_3CH_2MgBr$

Question 7

Which of the following statements best explains why the product with a tert-butyl group is not formed in the reaction of methyl chloride with tert-butylbenzene and $HCl$?

Accepted Answer

Steric hindrance prevents the formation of the tert-butyl carbocation

Question 8

Which compound has a higher boiling point: 1-butanol or 1-butanethiol? Justify your answer.

Accepted Answer

1-butanol, due to stronger hydrogen bonding ($O-H$ vs $S-H$)

Question 9

In the following reaction, which is the nucleophile?
$RSH + KOH \rightarrow RS^- + K^+ + H_2O$
$RS^- + R'Cl \rightarrow RSR' + KCl$

Accepted Answer

$RS^-$

Question 10

What is the purpose of running a reaction at pH 5 when synthesizing a hemiaminal from a carbonyl and an amine?

Accepted Answer

To protonate the carbonyl since the amine is not very nucleophilic

Question 11

Which of the following routes would successfully synthesize the target product (2-ethanol-1-ethylcyclohexane) from 1-bromoethylcyclohexane?

Accepted Answer

1) $NaH$ 2) $NaSEt$

Question 12

Which of the following is the correct curved arrow mechanism for the nucleophilic addition of $Et_2NH$ to a carbonyl at pH 5?

Accepted Answer

Arrow from $Et_2NH$ lone pair to carbonyl carbon, arrow from carbonyl double bond to oxygen

Question 13

Which intermediate is formed after nucleophilic addition of $Et_2NH$ to a carbonyl compound?

Accepted Answer

$R_2N-CH_2-OH$ (hemiaminal)

Question 14

Which of the following reagents would you use to convert a primary alcohol to an aldehyde?

Accepted Answer

$PCC$ in $CH_2Cl_2$

Question 15

Which of the following statements best explains why the product with a methyl group is not formed in the reaction of methyl chloride with tert-butylbenzene and $HCl$?

Accepted Answer

The reaction is not possible due to lack of carbocation rearrangement

Question 16

Which of the following is the correct product of a Wittig reaction between cyclohexanone and methyltriphenylphosphonium ylide?

Accepted Answer

Cyclohexylidene ($C_6H_{10}=CH_2$)

Question 17

Which of the following statements is true regarding the boiling points of alcohols and thiols?

Accepted Answer

Alcohols have higher boiling points than thiols due to hydrogen bonding

Organic Chemistry II: Midterm Exam Study Guide – Mechanisms, Synthesis, and Reactivity

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