Transcript CH 6-5 Power Point

CH 6-5 SN1 Reaction – Part II
Alkyl Halide Structure in SN1 Reactions
•Rank the following substrates in order of SN1 reactivity:
CH3
CH3
CH3
Br
CH3 CH2
Br
CH
Br
CH3 C
CH3
(NR)
Methyl, 1o
R

Lg

R
R
-
<<<<<
2o
Br
CH3
<<
3o
Trend is consistent with
carbonium ion stability.
Stereochemistry in The SN1 Reaction
A Non-Stereospecific Reaction
Racemic
“Racemization”………………….WHY?
The Leaving Group in SN1 Reactions
Since ionization of the substrate (i.e., the leaving group
“leaves” on its own), the Leaving Group is very important
in SN1 reactions, and MUST form a weak base:
F- <<<<
Cl-
<
R

Lg

R
Br-
R
-
<
I-
The Nucleophile in SN1 Reactions
•What are the most reactive nucleophiles in SN1 reactions?
ts1
ts2
Rate = k [substrate]
E
intermediate
R
P
Reaction Progress
•Neither the strength or concentration of the nucleophile
have any effect on the rate of SN1 reactions!
•SN1 reactions typically use weak nucleophiles, and the
solvent is often the source of the nucleophile – “solvolysis”
reactions are SN1 reactions.