Question 1

Which statement best explains why the carbon-carbon double bond in ethylene is shorter than the carbon-carbon single bond in ethane?

Accepted Answer

The overlap of sp\^2 hybrid orbitals in ethylene brings the carbon atoms closer, resulting in a bond length of $1.33\ 	ext{\AA}$ compared to $1.54\ 	ext{\AA}$ in ethane.

Question 2

What is the molecular geometry around each carbon atom in ethylene ($\ce{C_2H_4}$)?

Accepted Answer

Trigonal planar

Question 3

Which of the following best describes the formation of the pi bond in ethylene?

Accepted Answer

It is formed by the side-to-side overlap of unhybridized p orbitals on each carbon atom.

Question 4

A compound with the formula $\ce{C_5H_8}$ is found. How many degrees of unsaturation does it have?

Accepted Answer

$2$

Question 5

Which of the following statements about cis-trans isomerism in alkenes is correct?

Accepted Answer

Cis-trans isomerism occurs only when each carbon of the double bond has two different substituents.

Question 6

Using the Cahn–Ingold–Prelog rules, what is the configuration of 1-bromo-1-chloropropene if the highest priority groups are on opposite sides of the double bond?

Accepted Answer

E

Question 7

Which of the following is true regarding the boiling points of cis- and trans-2-butene?

Accepted Answer

Cis-2-butene has a higher boiling point because it is more polar than trans-2-butene.

Question 8

Which of the following best describes Zaitsev's Rule in elimination reactions?

Accepted Answer

The most substituted alkene is the major product.

Question 9

A student is asked to synthesize an alkene from 2-bromopropane using a strong base. Which mechanism is most likely to occur?

Accepted Answer

E2 elimination

Question 10

Which of the following statements about the E2 elimination mechanism is correct?

Accepted Answer

The leaving group and the hydrogen to be abstracted must be anti-coplanar for the reaction to occur.

Question 11

Which of the following would favor the formation of the Hofmann product in an E2 elimination?

Accepted Answer

Using a bulky base such as tert-butoxide.

Question 12

Which of the following is a correct application of Bredt’s Rule?

Accepted Answer

A bridged bicyclic compound cannot have a double bond at the bridgehead unless one of the rings contains at least eight carbon atoms.

Question 13

Which of the following is the correct formula to calculate the number of hydrogens in a saturated hydrocarbon containing $C$ carbons and $N$ nitrogens?

Accepted Answer

$2C + 2 + N$

Question 14

Which of the following statements about the physical properties of alkenes is correct?

Accepted Answer

Branched alkenes have lower boiling points than their straight-chain counterparts.

Question 15

During the acid-catalyzed dehydration of an alcohol to form an alkene, which step is rate-determining?

Accepted Answer

Ionization to form a carbocation

Question 16

Which of the following is a commercial use of ethylene?

Accepted Answer

Production of ethylene glycol

Question 17

A compound with the formula $\ce{C_6H_7N}$ is analyzed. How many degrees of unsaturation does it have?

Accepted Answer

$4$

Question 18

Which of the following statements about the stability of cycloalkenes is correct?

Accepted Answer

Cis-cycloalkenes are generally more stable than trans-cycloalkenes in small rings.

Question 19

Which of the following is true regarding the heat of hydrogenation of alkenes?

Accepted Answer

The more substituted the double bond, the lower its heat of hydrogenation.

Structure and Synthesis of Alkenes: Study Notes

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