replaced by chlorine are not large ⇒ chlorine does not discriminate among the
different types of hydrogen atoms to render chlorination of higher alknaes a
generally useful laboratory synthesis.
10.6A SELECTIVITY OF BROMINE
- Bromine is less reactive toward alkanes in general than chlorine, but bromine is
more selective in the site of attack when it does react.
- The reaction of isobutene and bromine gives almost exclusive replacement of the
3° hydrogen atom.
CH 3 CCH 2 H
CH 3
H
CH 3 CCH 3
CH 3
CH 3 CHCH 2 Br
CH 3
+
Br
(>99%) (trace)
Br 2
light, 127 oC
i) The ratio for chlorination of isobutene:
CH 3 CCH 2 H
CH 3
H
CH 3 CCH 3
CH 3
CH 3 CHCH 2 Cl
Cl
Cl 2 CH^3
+
(37%) (63%)
hν, 2 5 oC
- Fluorine is much more reactive than chlorine ⇒ fluorine is even less selective
than chlorine.
10.7 THE GEOMETRY OF ALKYL RADICALS
- The geometrical structure of most alkyl radicals is trigonal planar at the carbon
having the unpaired electron.
- In an alkyl radical, the p orbital contains the unpaired electron.
