Q: Which of the following statements about IR spectroscopy is correct?

Alcohols show broad absorption near $3300 \, \text{cm}^{-1}$

Question 1

Which IR absorption frequency is most characteristic of a carbonyl (C=O) stretch in a ketone?

Accepted Answer

$\sim 1710 \, 	ext{cm}^{-1}$

Question 2

A reaction converts a secondary alcohol to a ketone. How should this transformation be classified?

Accepted Answer

Oxidation

Question 3

Given the following reaction coordinate diagram with three transition states (TS1, TS2, TS3), which step is rate-limiting?

Accepted Answer

The step with the highest activation energy (TS2)

Question 4

What is the overall enthalpy change ($\Delta H$) for a reaction with the following steps: 1st step $\Delta H = -8$ kcal/mol, 2nd step $\Delta H = -10$ kcal/mol, 3rd step $\Delta H = -14$ kcal/mol?

Accepted Answer

$\Delta H = -32$ kcal/mol

Question 5

When 2-methylbutane is treated with Br$_2$ and light, which carbon is most likely to be brominated?

Accepted Answer

The tertiary carbon (carbon 2)

Question 6

Which reagent is best for reducing an ester to a primary alcohol?

Accepted Answer

LiAlH$_4$

Question 7

In a free-radical halogenation, which step determines the selectivity of the major product?

Accepted Answer

Propagation

Question 8

A student tries to convert an alcohol to a tosylate but overheats the reaction, isolating a chloride instead. What is the most likely mechanism for this transformation?

Accepted Answer

SN1 substitution via carbocation intermediate

Question 9

Which of the following reagents will oxidize a primary alcohol to an aldehyde but not further to a carboxylic acid?

Accepted Answer

PCC (Pyridinium chlorochromate)

Question 10

In the synthesis of 1-phenyl-1-cyclohexanol from benzene and cyclohexanone, which intermediate is formed after the Grignard reagent reacts with the ketone?

Accepted Answer

A tertiary alcohol

Question 11

Which of the following statements about IR spectroscopy is correct?

Accepted Answer

Alcohols show broad absorption near $3300 \, 	ext{cm}^{-1}$

Question 12

Which reagent would you use to convert a primary alcohol to a carboxylic acid?

Accepted Answer

Jones reagent (CrO$_3$, H$_2$SO$_4$)

Question 13

What is the major product when 2-butanol is treated with PBr$_3$?

Accepted Answer

2-bromobutane

Question 14

Which of the following transformations is a reduction?

Accepted Answer

Conversion of an alkene to an alkane

Question 15

A mixture of enantiomers is obtained when 2-butanol is converted to 2-bromobutane using which reagent?

Accepted Answer

HBr

Question 16

Which of the following is the best method to synthesize an ether from a primary alcohol?

Accepted Answer

Williamson ether synthesis

Question 17

Which of the following is true about the propagation steps in a free-radical halogenation?

Accepted Answer

They involve the formation and consumption of radicals

Question 18

What is the expected IR absorption for a C-H stretch in an alkane?

Accepted Answer

$\sim 3000 \, 	ext{cm}^{-1}$

Question 19

Which of the following best describes the role of LiAlH$_4$ in organic synthesis?

Accepted Answer

It reduces esters, carboxylic acids, and aldehydes to alcohols

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