Question 1

Which of the following best describes the role of a nucleophile in an organic reaction?

Accepted Answer

A nucleophile donates an electron pair to an electrophile to form a new chemical bond.

Question 2

In the addition of HBr to ethylene, which intermediate is formed during the reaction mechanism?

Accepted Answer

A carbocation intermediate

Question 3

Which of the following statements about carbon–carbon bonds in ethylene is correct?

Accepted Answer

The $$\pi$$ bond is weaker and its electrons are more accessible to electrophiles than the $$\sigma$$ bond.

Question 4

Which of the following is a correct application of the curved arrow notation in polar reaction mechanisms?

Accepted Answer

Curved arrows show the movement of electron pairs from nucleophiles to electrophiles.

Question 5

Which of the following species is most likely to act as an electrophile in a chemical reaction?

Accepted Answer

$$\mathrm{CH_3Br}$$

Question 6

In the reaction of chlorine with methane to produce chloromethane, what type of reaction mechanism is involved?

Accepted Answer

A radical chain reaction

Question 7

Which of the following best describes a radical in organic chemistry?

Accepted Answer

A species with an atom that has an odd number of electrons in its valence shell.

Question 8

According to the octet rule, what must occur if an electron pair moves to an atom that already has an octet?

Accepted Answer

Another electron pair must simultaneously move from that atom to maintain the octet.

Question 9

Which of the following is the correct expression for the equilibrium constant $$K_{eq}$$ for the reaction $$aA + bB \rightleftharpoons cC + dD$$?

Accepted Answer

$$K_{eq} = \frac{[C]^c[D]^d}{[A]^a[B]^b}$$

Question 10

Which of the following is a correct statement about the reaction between ethylene and HBr?

Accepted Answer

The $$\pi$$ electrons of ethylene attack the hydrogen atom of HBr, forming a carbocation intermediate.

Question 11

Which of the following is a correct description of a Lewis acid?

Accepted Answer

A Lewis acid is an electron pair acceptor and acts as an electrophile.

Question 12

In a radical reaction, which of the following is true about the movement of electrons?

Accepted Answer

A single-headed arrow is used to show the movement of a single electron.

Question 13

Which of the following best explains why alkenes are more reactive toward electrophiles than alkanes?

Accepted Answer

The $$\pi$$ electrons in alkenes are more accessible and less tightly held than the $$\sigma$$ electrons in alkanes.

Question 14

Which of the following is a plausible nucleophile in an organic reaction?

Accepted Answer

$$\mathrm{Cl^-}$$

Question 15

In the mechanism of the addition of HBr to ethylene, what is the role of the bromide ion ($$\mathrm{Br^-}$$)?

Accepted Answer

It donates an electron pair to the carbocation to form the C–Br bond.

Question 16

Which of the following is a correct statement about chemical equilibrium?

Accepted Answer

If $$K_{eq} is $$near 1, appreciable amounts of both reactant and product are present at equilibrium.

Question 17

Which of the following best describes the flow of electrons in a polar reaction mechanism?

Accepted Answer

Electrons flow from a nucleophilic source to an electrophilic sink.

Question 18

Which of the following is a real-world application of a radical reaction discussed in the study materials?

Accepted Answer

The industrial synthesis of chloromethane from methane and chlorine.

Chapter 6: An Overview of Organic Reactions – Electrophiles, Nucleophiles, Polar and Radical Mechanisms

Study Guide - Practice Questions