Question 1

Which of the following best describes the lowest energy conformation of butane?

Accepted Answer

The anti conformation where the two methyl groups are $$180^{\circ}$$ apart.

Question 2

Which of the following is true about the index of hydrogen deficiency (IHD) for a compound with the empirical formula $$C_4H_7NO_2$$?

Accepted Answer

$$	ext{IHD} = 2$$

Question 3

A sample contains 7 moles of the S enantiomer and 3 moles of the R enantiomer. What is the enantiomeric excess of the S enantiomer?

Accepted Answer

$$70\%$$

Question 4

Which of the following solvents is best for an $$S_N2$$ reaction?

Accepted Answer

Polar aprotic

Question 5

What is the major product of the $$S_N1$$ substitution of tert-butyl chloride in ethanol?

Accepted Answer

tert-butyl alcohol

Question 6

Which of the following best describes the relationship between the pair of compounds shown below (one is (R,R)-2,3-butanediol and the other is (S,S)-2,3-butanediol)?

Accepted Answer

Enantiomers

Question 7

Which of the following is NOT chiral?

Accepted Answer

A meso compound

Question 8

What is the correct IUPAC name for the following structure: a seven-carbon chain with a chlorine on carbon 2 and methyl groups on carbons 2 and 6?

Accepted Answer

2-chloro-2,6-dimethylheptane

Question 9

Which of the following mechanisms correctly describes an $$S_N2$$ reaction?

Accepted Answer

The nucleophile attacks and the leaving group leaves simultaneously in the same step.

Question 10

Which of the following reactions will be fastest for an $$S_N2$$ mechanism?

Accepted Answer

Reaction with a primary alkyl bromide in polar aprotic solvent

Question 11

What is the configuration (R or S) of the carbon atom indicated by the dot in the following structure (where the priorities are: OH \u003e COOH \u003e H \u003e CH$$_3$$)?

Accepted Answer

S

Question 12

Which of the following is a constitutional isomer of $$C_3H_7NO_2$$?

Accepted Answer

A molecule with a different connectivity but same molecular formula

Question 13

What is the index of hydrogen deficiency (IHD) for the following compound: cyclopentanone?

Accepted Answer

$$	ext{IHD} = 2$$

Question 14

Which of the following is the correct product of the reaction: $$\mathrm{BrCH_2CH_2OCH_3}$$ with $$\mathrm{KCN} in $$DMSO?

Accepted Answer

$$\mathrm{NCCH_2CH_2OCH_3}$$

Question 15

Which of the following is true about the intermediate formed after an intramolecular $$S_N2$$ attack on 1,3-dichloropropane?

Accepted Answer

A three-membered ring (cyclopropane) is formed.

Question 16

Which of the following is the correct priority numbering of substituents on a cyclohexane ring with OH at carbon 1, COOH at carbon 2, and H at carbon 4?

Accepted Answer

1: COOH, 2: OH, 3: H

Question 17

Which of the following is the correct mechanism for the intramolecular substitution reaction of 6-chlorohexanol with NaOH?

Accepted Answer

The hydroxide attacks the carbon bearing the chlorine, forming a six-membered ring and releasing Cl$$^-.$$

Question 18

Which of the following is the correct product of the substitution reaction of cyclohexyl chloride with HS$$^- in $$DMF?

Accepted Answer

Cyclohexyl thiol

Question 19

Which of the following is the correct structure resulting from a reaction of cyanide and bromoethane that proceeds by an $$S_N2$$ mechanism?

Accepted Answer

$$\mathrm{NCCH_2CH_3}$$

Organic Chemistry: Conformations, Stereochemistry, and Substitution Mechanisms Study Guide

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