Which reacts faster in an S_N2 reaction?

Draw a perspective structure or a Fischer projection for the products of the following S_N2 reactions.

(c)

(d)

Predict the major products of the following reactions.

(d) the tosylate of cyclohexylmethanol + excess NH₃

(e) n-butyl tosylate + sodium acetylide, H–C≡C:^{– +}Na

Rank the following compounds in decreasing order of their reactivity toward the S_N2 reaction with sodium ethoxide (Na^{+ –}OCH₂CH₃) in ethanol.

methyl chloride

tert-butyl iodide 

neopentyl bromide

isopropyl bromide

methyl iodide

ethyl chloride

When (±)−2,3−dibromobutane reacts with potassium hydroxide, some of the products are (2S,3R)-3-bromobutan-2-ol and its enantiomer and trans-2-bromobut-2-ene. Why is no cis-2-bromobut-2-ene formed?

Explain why the alkyl halide shown here reacts much more rapidly with guanine than does a primary alkyl halide (such as pentyl chloride).

Under appropriate conditions, (S)-1-bromo-1-fluoroethane reacts with sodium methoxide to give pure (S)-1-fluoro-1-methoxyethane.

a. Why is bromide rather than fluoride replaced?

b. Draw perspective structures (as shown on the previous page for 2-bromobutane) for the starting material, the transition state, and the product.

c. Does the product show retention or inversion of configuration? d. Is this result consistent with reaction by the SN2 mechanism?

Which of the following S_N2 reactions should proceed at a faster rate? Justify your answer on a reaction coordinate diagram.

What stereoisomers do the following reactions form?

d.