Question 1

Which of the following best describes the mechanism for the acid-catalyzed dehydration of cyclohexylethanol to form 1-ethylcyclohexene?

Accepted Answer

E1 elimination involving carbocation formation, followed by a 1,2-hydride shift and loss of a proton

Question 2

Given the following pairs of alkenes, which is more stable: cyclohexene vs. 1-hexene? Use $$\sigma$$ and $$\pi$$ bond considerations.

Accepted Answer

Cyclohexene, because it is a cyclic alkene with less ring strain and more substituted double bond

Question 3

In the dissolving metal reduction of 2-hexyne with lithium in liquid ammonia, what is the major product and its stereochemistry?

Accepted Answer

trans-2-hexene

Question 4

Which reagent is used to convert an alkyne to a trans-alkene via dissolving metal reduction?

Accepted Answer

$$\mathrm{Na} or$$ $$\mathrm{Li} in$$ $$\mathrm{NH}_3 ($$liq)

Question 5

During oxymercuration-demercuration of methylcyclohexene, which intermediate is formed after reaction with $$\mathrm{Hg(OAc)_2} in $$water?

Accepted Answer

A mercurinium ion bridged intermediate

Question 6

What is the expected product when 1-bromocyclopentene is treated with $$\mathrm{$$NaNH_2$$} in $$excess?

Accepted Answer

Cyclopentyne

Question 7

A compound with formula $$\mathrm{C_7H_7BrO} is $$synthesized. Using the exact masses $$\mathrm{^{12}C}$$: 12.0000, $$\mathrm{^1H}$$: 1.0078, $$\mathrm{^{79}Br}$$: 78.9183, $$\mathrm{^{16}O}$$: 15.9949, what is the expected molecular ion mass?

Accepted Answer

$$197.9680$$

Question 8

Which of the following best explains the regioselectivity observed in the E2 elimination of 2-bromo-3-methylpentane with a bulky base?

Accepted Answer

The base removes the most accessible proton, favoring the less substituted alkene (Hofmann product)

Question 9

Which IR absorption is characteristic of a carbonyl group ($$\mathrm{C=O}$$)?

Accepted Answer

$$1700-1750\ \mathrm{cm}^{-1}$$

Question 10

In $$^1H $$NMR, what is the expected multiplicity for the bolded hydrogen in the following structure: $$\mathrm{CH_3CH_2OH} ($$ethanol), assuming only 3-bond coupling?

Accepted Answer

Triplet

Question 11

Which of the following reactions will convert cyclopentene to cyclopentanol?

Accepted Answer

$$\mathrm{BH_3$}$$, THF; $$\mathrm{H_2O_2}$$, $$\mathrm{OH^-}$$

Question 12

What is the major product when 2-pentyne is treated with $$\mathrm{H_2$}$$ and Lindlar catalyst?

Accepted Answer

cis-2-pentene

Question 13

Which of the following best describes the role of $$\mathrm{$$NaBH_4$$} in $$oxymercuration-demercuration?

Accepted Answer

It reduces the organomercury intermediate to form the alcohol

Question 14

Which of the following is the expected product when methylcyclopentene reacts with chloroform and potassium tert-butoxide?

Accepted Answer

A dichlorocyclopropane derivative

Question 15

Which of the following statements about the IR spectrum of 2-pentanone is correct?

Accepted Answer

It shows a strong absorption near $$1700\ \mathrm{cm}^{-1}$$ due to the $$\mathrm{C=O}$$ stretch

Question 16

Which of the following best explains the difference in product formation between slow and fast E2 elimination of 2-bromo-3-methylpentane?

Accepted Answer

Slow E2 allows for anti-periplanar geometry, favoring the more substituted alkene

Question 17

Which of the following is the correct chemical shift range for a methyl group ($$\mathrm{$$RCH_3$$}) in$$ $$^{1}H $$NMR?

Accepted Answer

$$0.9-1.0$$

Question 18

What is the expected multiplicity for the bolded hydrogen in the following structure: $$\mathrm{CH_3CH_2CH_2OH} (1-$$propanol), assuming only 3-bond coupling?

Accepted Answer

Quartet

Question 19

Which of the following reagents would convert a cyclopentene to a cis-1,2-diol?

Accepted Answer

$$\mathrm{$$OsO_4$$}$$, $$\mathrm{$$NaHSO_3$$}$$

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