Question 1

Which of the following compounds would produce the 1H NMR spectrum shown in the first image (with peaks at approximately 7.2, 2.4, and 1.2 ppm, with integrations 5:1:6)?

Accepted Answer

Ethylbenzene ($$C_6H_5CH_2CH_3)$$

Question 2

The second NMR spectrum shows three types of protons with integrations 2:2:3:2:2. Which compound best matches this spectrum?

Accepted Answer

1,4-Dimethylbenzene (p-xylene)

Question 3

In the molecule shown (third image), which C-H bond (labeled a–e) is expected to have the lowest bond dissociation energy?

Accepted Answer

$$\mathrm{C-H_c}$$

Question 4

The structure shown in the fourth image is best described as:

Accepted Answer

Bicyclo[2.2.1]hept-2-ene (norbornene)

Question 5

In the Diels-Alder reaction shown in the fifth image, which product (I–V) is expected to be the major product?

Accepted Answer

IV

Question 6

Which of the following best describes the type of π bonds in zingiberene (see image with labeled I, II, III)?

Accepted Answer

I = isolated; II = conjugated; III = conjugated

Question 7

Rank the dienes shown (last image) in order of increasing stability (least to most).

Accepted Answer

$$\mathrm{II \u003c III \u003c I}$$

Question 8

Which product is expected from the reaction of 1,4-dimethylcyclohexene with HBr (see image 8 and 9)?

Accepted Answer

III

Question 9

When 1,2-dibromocyclohexane is treated with potassium tert-butoxide, which product is formed (see image 10 and 11)?

Accepted Answer

III

Question 10

Which of the following statements about the NMR spectrum of ethylbenzene is correct?

Accepted Answer

The methylene group appears as a quartet around 2.6 ppm.

Question 11

Which of the following best explains why the C-H bond labeled 'c' in the cyclopentene derivative (third image) has the lowest bond dissociation energy?

Accepted Answer

It is allylic to a double bond, stabilizing the radical formed upon homolysis.

Question 12

Which of the following is the best description of the product formed when 1,2-dibromocyclohexane reacts with potassium tert-butoxide?

Accepted Answer

A conjugated diene

Question 13

Which of the following is a correct statement about the Diels-Alder reaction shown in the fifth image?

Accepted Answer

The reaction forms a bicyclic product with cyano groups at the 2,3-positions.

Question 14

Which of the following best describes the effect of conjugation on the stability of dienes (see last image)?

Accepted Answer

Conjugated dienes are more stable than cumulated dienes.

Question 15

Which of the following is the best explanation for the splitting pattern observed at 2.6 ppm in the NMR spectrum of ethylbenzene?

Accepted Answer

It is a quartet due to coupling with three methyl protons.

Organic Chemistry Practice Exam Guidance – NMR, Bond Strength, and Reaction Mechanisms

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