Q: Which of the following molecules has the greatest number of elements of unsaturation, based on the eighth image?

$$\text{CH}\equiv\text{C}-\text{CH}_3 ($$propyne)

Q: Which of the following bases would most likely lead to the formation of the Hofmann product in an elimination reaction, as shown in the twenty-fourth image?

tert-Butoxide ion ($$\text{(CH}_3)_3\text{CO}^-)$$

Question 1

Which of the following statements best describes the bonding in ethylene (C2H4) as shown in the first image?

Accepted Answer

The double bond consists of one sigma bond and one pi bond, with the sigma bond formed by sp2-sp2 overlap and the pi bond formed by side-to-side overlap of unhybridized p orbitals.

Question 2

Based on the bond lengths and angles shown in the second image, which statement is correct regarding the geometry of ethylene compared to ethane?

Accepted Answer

Ethylene has a bond angle of $$121.7^\circ$$ and a C–C bond length of $$1.33\ 	ext{Å}$$, indicating sp2 hybridization and a shorter, stronger double bond.

Question 3

Refer to the third image. What is the hybridization of the carbon atoms in ethylene, and how does this relate to the formation of the pi bond?

Accepted Answer

Both carbons are sp2 hybridized, and the pi bond is formed by the side-to-side overlap of the remaining unhybridized p orbitals.

Question 4

Which of the following best explains why rotation around the carbon–carbon double bond in alkenes is restricted, as illustrated in the fourth image?

Accepted Answer

The pi bond, formed by side-to-side overlap of p orbitals, would be broken upon rotation, making the double bond rigid.

Question 5

Based on the bond dissociation enthalpies shown in the sixth image, which statement is correct?

Accepted Answer

The C=C double bond in ethylene is stronger than the C–C single bond in ethane, as indicated by the higher bond dissociation enthalpy.

Question 6

Which of the following molecules has the greatest number of elements of unsaturation, based on the eighth image?

Accepted Answer

$$	ext{CH}\equiv	ext{C}-	ext{CH}_3 ($$propyne)

Question 7

Which of the following is a constitutional isomer of but-1-ene, as shown in the ninth image?

Accepted Answer

But-2-ene

Question 8

Which of the following alkenes can exhibit cis/trans (geometric) isomerism, as illustrated in the tenth image?

Accepted Answer

2-butene

Question 9

According to the Cahn-Ingold-Prelog priority rules (see image 11), which group has the highest priority?

Accepted Answer

$$-	ext{CH}=	ext{O}$$

Question 10

Which of the following compounds has the highest dipole moment, based on the thirteenth image?

Accepted Answer

cis-1-chloro-2-butene

Question 11

Based on the heat of combustion data in the fifteenth image, which alkene is the most stable?

Accepted Answer

2-methyl-2-butene

Question 12

Which of the following best describes the mechanism of the E2 elimination reaction shown in the eighteenth image?

Accepted Answer

It is a concerted, one-step process where the base abstracts a proton as the leaving group departs.

Question 13

Which of the following bases would most likely lead to the formation of the Hofmann product in an elimination reaction, as shown in the twenty-fourth image?

Accepted Answer

tert-Butoxide ion ($$	ext{(CH}_3)_3	ext{CO}^-)$$

Question 14

Which statement about the stereochemistry of the E2 elimination reaction is correct, as illustrated in the twenty-sixth image?

Accepted Answer

The E2 reaction is stereospecific and typically proceeds via an anti-coplanar transition state.

Question 15

Which of the following statements best explains why tertiary alkyl halides are better substrates for E2 elimination than for SN2 substitution, as shown in the twenty-second image?

Accepted Answer

Tertiary alkyl halides are too hindered for SN2, but a strong base can abstract a proton for E2 elimination.

Question 16

Which of the following is the major product when 2-bromo-2-methylbutane is treated with potassium tert-butoxide, as shown in the twenty-fifth image?

Accepted Answer

The least substituted alkene (Hofmann product)

Question 17

Which of the following best describes the rate law for an E1 elimination reaction?

Accepted Answer

$$	ext{Rate} = k[	ext{substrate}]$$

Question 18

Which of the following statements about Zaitsev’s rule is correct, as shown in the nineteenth image?

Accepted Answer

The most substituted alkene is usually the major product in elimination reactions.

Structure and Preparation of Alkenes: Elimination Reactions

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