Quiz | Properties and Reactions of Haloalkanes

1

Which of the following bonds has the greatest bond dipole moment?

H-F

H-Cl

H-Br

H-I

Fluorine is the most electronegative halogen atom. The difference of electronegativity between fluorine and carbon is the greatest ⇒ H-F has the greatest bond dipole moment

2

Which statement is incorrect about the reaction of 1-bromobutane and hydroxide ion?

The leaving group is Br-

The reaction proceeds via two steps

The reaction is accompanied by inversion of configuration

The kinetic rate involves both reactants

1-bromobutane is an haloalkane with a good leaving halogen atom (Br-)
Hydroxide ion HO- is a good nucleophile
The reaction between 1-bromobutane and HO- is a SN2 which do not proceed via an intermediate ⇒ the reaction proceeds via only one step

3

Which of the following group is not a good leaving group?

Br-

TsO-

I-

HO-

HO-​​​​​​​ is not a good leaving group but a good nucleophile

4

Which of the following is least likely to undergo an SN2 reaction?

CH3Br

CH3CH2​​​​​​​Br

(CH3)2CHBr

(CH3)3CBr

Steric effects are particularly important in SN2 reactions: the greater the steric hindrance around the reaction center, the less reactive the compound

5

Which statement is incorrect?

Rates of nucleophilic substitution are affected by steric effects

Inversion of configuration means inversion of the absolute configuration of the chiral center

SN2 reactions are favored when attack by the nucleophile is sterically unhindered

The nucleophile attacks the electrophile center on the opposite side of the good leaving group

During a SN2 reaction, the nucleophile attacks the electrophile center on the opposite side of the good leaving group. The other substituents flip from one side to the other: this is the inversion of configuration. However, inversion of configuration does not mean inversion of the absolute configuration of the chiral center

6

Which of the following nucleophiles is the best?

NC-

HO-

Cl-

H2O

NCis electron-rich and the negative charge is on the carbon atom. Carbon is less electronegative than oxygen and chlorine ⇒ NC- is a stronger nucleophile than HO- and Cl-
H2O is not electron-rich ⇒ it is not a good nucleophile