Question 1

Which of the following best describes the product of the hydroboration-oxidation of 1-methylcyclopentene using $$1) \mathrm{BH}_3, \mathrm{THF} \ 2) \mathrm{H}_2\mathrm{O}_2, \mathrm{NaOH}$$?

Accepted Answer

A cyclopentanol with the hydroxyl group on the less substituted carbon (anti-Markovnikov addition)

Question 2

A compound shows two strong IR peaks around $$1720\ \mathrm{cm}^{-1}$$ and $$3070\ \mathrm{cm}^{-1}$$, and a broad peak at $$3400\ \mathrm{cm}^{-1}. $$Which functional groups are most likely present?

Accepted Answer

Ketone and alcohol

Question 3

Which of the following best explains why the product of the reaction of 1,2-dibromocyclopentane with heat is optically inactive?

Accepted Answer

The product is a racemic mixture of enantiomers in equilibrium

Question 4

How many stereoisomers are possible for a compound with 4 asymmetric centers and no internal plane of symmetry?

Accepted Answer

$$2^4 = 16$

Question 5

Which of the following statements is true regarding the optical activity of meso-tartaric acid?

Accepted Answer

It is optically inactive because it is a meso compound

Question 6

Which IR spectrum would you expect for a compound containing a nitrile group ($$\mathrm{C} \equiv \mathrm{N}$$)?

Accepted Answer

A strong absorption near $$2250\ \mathrm{cm}^{-1}$$

Question 7

For the equilibrium between two chair conformers of methylcyclohexane, which conformer is thermodynamically favored?

Accepted Answer

The conformer with the methyl group in the equatorial position

Question 8

When 1,2-dideutero-1,2-diphenylethene is reduced with diimide, what is the stereochemistry of the product?

Accepted Answer

Syn addition of hydrogen atoms

Question 9

If 1 mole of the alkene shown reacts completely with one mole of diimide, would the product mixture be optically active or inactive? Explain.

Accepted Answer

Optically inactive, because the product is a meso compound

Question 10

What is the most stable Lewis structure for diimide ($$\mathrm{N}_2\mathrm{H}_2$$)?

Accepted Answer

A structure with a double bond between the two nitrogens and each nitrogen bonded to one hydrogen

Question 11

Given the following equilibrium: $$\mathrm{A} \rightleftharpoons \mathrm{B}$$, and $$\Delta G$$ for A to B is about $$+5.5\ \mathrm{kJ\ mol}^{-1}$$, what is the approximate $$K_{eq}$$ for the equilibrium?

Accepted Answer

$$0.1$$

Question 12

Bromine reacts with 3-ethylcyclopentene in carbon tetrachloride to form what?

Accepted Answer

Two enantiomers in equal amounts

Question 13

A sample of the pure S enantiomer of a compound has a specific rotation of $$+80^\circ. $$What is the specific rotation of another sample containing 20% of this compound and 80% of its enantiomer?

Accepted Answer

$$-48^\circ$$

Question 14

How many stereocenters exist in the following molecule (cyclohexane ring with two substituents at 1 and 3 positions, both different)?

Accepted Answer

3

Question 15

What is the relationship between the following two compounds: $$\mathrm{HOCH}_2\mathrm{CH}_2\mathrm{CH}_2\mathrm{OH}$$ and $$\mathrm{HOCH}_2\mathrm{CH}(	ext{OH})\mathrm{CH}_3$$?

Accepted Answer

Constitutional isomers

Question 16

Which of the following best describes the mechanism for the hydrogenation of an alkene with diimide?

Accepted Answer

Syn addition of hydrogen atoms with no rearrangements or carbocation intermediates

Question 17

Which of the following statements is true for the reaction of $$(+)-3-$$methylcyclohexene with $$\mathrm{OsO}_4$$ and $$\mathrm{H}_2\mathrm{O}_2$$?

Accepted Answer

The products are diastereomers formed in unequal amounts

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