Question 1

Consider the following reaction:

$$\mathrm{(CH_3$)_2CHCHBrCH_2CH_3} \xrightarrow{\mathrm{$$NaOCH_3$$,\ $$HOCH_3$$,\ heat}}$$

What is the major organic product?

Accepted Answer

An alkene formed by E2 elimination at the most substituted position: $$\mathrm{(CH_3$)_2C=CHCH_2CH_3}$$

Question 2

A cyclohexyl bromide with trans substituents reacts with $$\mathrm{$$NaOCH_3$$} in$$ $$\mathrm{$$HOCH_3$$}$$ and heat. What is the expected major product?

Accepted Answer

A trans-alkene formed by anti-periplanar elimination: $$\mathrm{trans	ext{-}1,2	ext{-}dimethylcyclohexene}$$

Question 3

Given the following sequence:

$$\mathrm{(CH_3$)_2CHCHBrCH=CH_2$} (Br is $$wedge) $$\xrightarrow{1.\ H_2$,\ Ni} \xrightarrow{2.\ EtOH,\ heat}$$

What is the final major product?

Accepted Answer

An alkene formed by E2 elimination after hydrogenation: $$\mathrm{(CH_3$)_2C=CHCH_2CH_3}$$

Question 4

A cyclohexanol undergoes the following sequence:

$$\mathrm{1.\ $$PBr_3$$,\ base\ \rightarrow\ 2.\ NaI\ \rightarrow\ 3.\ EtONa,\ EtOH}$$

What is the final product?

Accepted Answer

A cyclohexene formed by E2 elimination of the iodide intermediate.

Question 5

Which of the following is NOT a method to convert an alcohol into a good leaving group?

Accepted Answer

Treating with $$\mathrm{NaOH}$$

Question 6

What is the rate law for an $$\mathrm{S_N2}$$ reaction?

Accepted Answer

$$\mathrm{rate = k[substrate][nucleophile]}$$

Question 7

What effect does resonance have on the positive charge of a benzylic carbocation?

Accepted Answer

Resonance delocalizes and stabilizes the positive charge over the aromatic ring.

Question 8

Which compound has the lowest $$\mathrm{p}K_a ($$strongest acid) among the following?

$$\mathrm{a)\ CH_3CH_2OH}$$
$$\mathrm{b)\ CH_3CO_2H}$$
$$\mathrm{c)\ HC \equiv CH}$$
$$\mathrm{d)\ CH_2$=CH_2$}$$
$$\mathrm{e)\ CH_3CH_3}$$

Accepted Answer

$$\mathrm{CH_3CO_2H}$$

Question 9

In the reaction $$\mathrm{C_6H_5OH + CH_3ONa \rightarrow C_6H_5ONa + CH_3OH}$$, which compound acts as the acid?

Accepted Answer

$$\mathrm{C_6H_5OH}$$

Question 10

Which of the following carboxylic acids is the strongest acid?

$$\mathrm{a)\ CH_3CH_2CH_2CH_2CHFCO_2H}$$
$$\mathrm{b)\ CH_3CHBrCH_2CH_2CH_2CO_2H}$$
$$\mathrm{c)\ CH_3CH_2CH_2CHClCH_2CO_2H}$$
$$\mathrm{d)\ CH_3CH_2CH_2CHFCH_2CO_2H}$$
$$\mathrm{e)\ CH_3CH_2CH_2CHICH_2CO_2H}$$

Accepted Answer

$$\mathrm{CH_3CHBrCH_2CH_2CH_2CO_2H}$$

Question 11

Which of the following is a meso compound?

Accepted Answer

Structure II (from the Fischer projections shown)

Question 12

Rank the following alcohols in decreasing order of acidity:

I: $$\mathrm{CH_3CH_2CH_2OH}
II$$: $$\mathrm{CH_3CH(OH)CH_3$}$$
III: $$\mathrm{(CH_3$)_3COH}$$

Accepted Answer

II \u003e I \u003e III

Question 13

What is the major product when 2-bromo-2-methylbutane reacts with methanol?

Accepted Answer

2-methoxy-2-methylbutane (via $$\mathrm{S_N1})$$

Question 14

Which of the following best describes the effect of doubling the solvent concentration in an $$\mathrm{S_N2}$$ reaction?

Accepted Answer

The rate decreases due to dilution of reactants.

Question 15

Which of the following is the correct resonance structure for the benzylic carbocation?

Accepted Answer

The positive charge is delocalized onto the ortho and para positions of the ring.

Question 16

Which of the following statements about the $$\mathrm{E2}$$ elimination mechanism is correct?

Accepted Answer

It requires an anti-periplanar arrangement of the leaving group and the hydrogen.

Question 17

Which of the following is the strongest acid?

$$\mathrm{a)\ CH_3CH_2OH}$$
$$\mathrm{b)\ CH_3CO_2H}$$
$$\mathrm{c)\ HC \equiv CH}$$
$$\mathrm{d)\ CH_2$=CH_2$}$$
$$\mathrm{e)\ CH_3CH_3}$$

Accepted Answer

$$\mathrm{CH_3CO_2H}$$

Question 18

Which of the following is the correct Newman projection for a compound with two methyl groups anti to each other?

Accepted Answer

Projection II

Predicting Products of Organic Reactions (E2 Elimination and Substitution)

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