Chem 334 - Summer 1998 - Organic Chemistry I Dr. Carl C. Wamser

Chapter 6 Homework Answers - Haloalkanes. Nucleophilic Substitution

Vollhardt & Schore, pp 201 -205
Problems 1 , 2 , 8 , 9 , 10 , 11 , 12 , 13 , 15 , 17 , 18 , 21 , 22

1. Arrange the following in order of nucleophilicity:

all the halide anions, OH- , H2O , HS-

(see Table 6-8, p 197)
HS- > I- > HO- > Br- > Cl- > F- > H2O

2. Arrange the same compounds as in problem 1 with respect to their leaving group ability.

(see Table 6-4, p 188)
I- > Br- > H2O > Cl- > F- > HS- > HO-

3. Arrange the following alkyl halides in order of their reactivity in an SN2 reaction:

bromomethane, 1-bromopropane, 2-bromopropane, chlorocyclohexane

(see Table 6-9, p 199)

4. Illustrate the mechanism of the SN2 reaction between trans-1-bromo-4-methyl-cyclohexane and CN-, specifically showing the stereochemistry of the reactants and the products.

How would the products differ if the starting material was optically active 1-bromo-4-methylcyclohexane?

It can't be optically active. A simple 1,4-disubstituted cyclohexane is achiral - there are no chiral centers, and the molecule has a plane of symmetry.

5. Write a complete mechanism for the SN2 cleavage of dimethyl ether (CH3OCH3) using concentrated HI.

Protonation of oxygen creates a good leaving group for iodide to displace.

Repeat to replace OH with I.

Overall: