Nucleophilic Substitution at a Saturated Carbon Atom
(vi) The formation of alkyl halides:
R-OH+H® -»• R-OH
H
BrQ + R-OH -*• BrR + HaO
H
(vii) The cleavage of ethers:
Ph OR+H® ->PhOR •
PhOR + I® PhOH+RI
H
(viii) The formation of esters:
R' • CO,® + RBr -*• R'-C0 2 R + Br©
(ix) The formation of ethers:
RO©+R'Br -fR'OR'+Br^9
m
(x) LiAIH 4 reduction of halides:
LfAlH.+RBr -* LiAlH 3 Br+HR
Here the complex hydride is, essentially, acting as a carrier for hydride
ion, H®, which is the effective nucleophile.
(xi) Ring fission in epoxides:
Cl^CHj—CH 2 -> ClCHjCHjO^9
C1CH 2 CH, Oe+H 2 0 C1CH, CH 2 OH+eOH
Here it is the relief of strain achieved on opening the three-membered
ring that is responsible for the ready attack by a weak* nucleophile.
This is only a very small selection: there are many more displace
ment reactions of preparative utility and synthetic importance.