Q: Which of the following reagent sets would best achieve the anti-dihydroxylation of an alkene?

$$1.\ \mathrm{m\text{-}CPBA}\ \quad 2.\ \mathrm{H_3O^+}$$

Question 1

Which of the following best describes a carbene?

Accepted Answer

A neutral molecule with a divalent carbon atom and two nonbonded electrons.

Question 2

Given the molecular formula $$\mathrm{C$$_{20}$$H_{20}F$$_{22}}$, is this compound saturated or unsaturated? Use the degree of unsaturation formula to justify your answer.

Accepted Answer

Unsaturated, because the degree of unsaturation is greater than zero.

Question 3

Which set of reagents would convert an alkene to an ether via oxymercuration-demercuration?

Accepted Answer

$$1.\ \mathrm{Hg(OAc)_2,\ CH_3OH}\ \quad 2.\ \mathrm{$$NaBH_4$$}$$

Question 4

A student wants to separate benzoic acid from methyl benzoate using liquid-liquid extraction. Which solvent should be used first to selectively extract benzoic acid into the aqueous layer?

Accepted Answer

Saturated aqueous sodium bicarbonate ($$\mathrm{sat.\ $$NaHCO_3$$})$$

Question 5

Which of the following statements about the TLC separation of benzoic acid and methyl benzoate is correct?

Accepted Answer

Methyl benzoate will have a higher $$R_f$$ value than benzoic acid.

Question 6

Which of the following reagent sets would best achieve the anti-dihydroxylation of an alkene?

Accepted Answer

$$1.\ \mathrm{m	ext{-}CPBA}\ \quad 2.\ \mathrm{H_3O^+}$$

Question 7

Which of the following best explains how to increase the yield of the thermodynamic product over the kinetic product in a reaction with two possible products?

Accepted Answer

Increase the reaction temperature to favor the more stable product.

Question 8

Which of the following is the correct IUPAC name for a molecule with a double bond between C-3 and C-4, a methyl group at C-3, and a bromo group at C-4 on a decene chain, with the higher priority groups on opposite sides?

Accepted Answer

E-4-bromo-3-methyl-3-decene

Question 9

A reaction of an alkene with $$\mathrm{CH_2I_2}$$ and $$\mathrm{Zn/Cu}$$ produces a cyclopropane ring. What is the reactive intermediate in this reaction?

Accepted Answer

A carbene

Question 10

Which of the following statements about the use of $$\mathrm{$$OsO_4$$}$$ and $$\mathrm{NMO} in $$alkene chemistry is correct?

Accepted Answer

They produce a syn-diol by adding two hydroxyl groups to the same side of the double bond.

Question 11

Which of the following best describes the product(s) of ozonolysis of an alkene followed by treatment with DMS?

Accepted Answer

Aldehydes and/or ketones, depending on the substitution of the alkene.

Question 12

In the mechanism of acid-catalyzed hydration of an alkene, which intermediate is formed after the first step?

Accepted Answer

A carbocation

Question 13

Which of the following is a correct step in the purification of benzoic acid from methyl benzoate using the provided reagents?

Accepted Answer

Extract the mixture with saturated $$\mathrm{$$NaHCO_3$$} to $$convert benzoic acid to its water-soluble sodium salt.

Question 14

Which of the following best describes the effect of using $$\mathrm{BD_3$\cdot THF}$$ instead of $$\mathrm{BH_3$\cdot THF} in $$hydroboration-oxidation of an alkene?

Accepted Answer

The product will have deuterium incorporated at the position where boron initially added.

Question 15

Which of the following is the correct order of steps for separating benzoic acid from methyl benzoate using the available reagents?

Accepted Answer

Extract with $$\mathrm{$$NaHCO_3$$}$$, acidify aqueous layer with HCl, filter precipitated benzoic acid.

Question 16

Which of the following best describes the product of syn-dihydroxylation of an alkene using $$\mathrm{$$OsO_4$$}$$ and $$\mathrm{NMO}$$?

Accepted Answer

A vicinal diol with both hydroxyl groups added to the same side of the double bond.

Question 17

Which of the following is a correct statement about the kinetic and thermodynamic products in a reaction?

Accepted Answer

The kinetic product forms faster but is less stable than the thermodynamic product.

Question 18

Which of the following best describes the effect of adding $$\mathrm{Br_2$} to an $$alkene in $$\mathrm{EtOH}$$?

Accepted Answer

Formation of a bromoether via anti addition.

Question 19

Which of the following is the correct sequence of steps in the mechanism for the acid-catalyzed addition of HBr to an alkene?

Accepted Answer

Protonation of the alkene to form a carbocation, followed by nucleophilic attack by Br$$^-.$$

Organic Chemistry Exam 4 – Step-by-Step Study Guidance

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