Advices For Studying Organic Chemistry

CC

H H

HC

H

H H Cl

Cl

3) Second Chain-propagating Step

CC

H H

HCH H

+ H

Allyl radical

Cl Cl

Cl

Cl

CC

H H

HCH 2

CC

H H

HCH 2

+

Allyl chloride

3. Bond dissociation energies of C–H bonds:
   CH 2 =CHCH 2 —H CH 2 =CHCH 2 • + H• ∆H° = 360 kJ mol–1
   Propene Allyl radical

(CH 3 ) 3 C—H (CH 3 ) 3 C• + H• ∆H° = 380 kJ mol–1
Isobutane 3° Radical

(CH 3 ) 2 CH—H (CH 3 ) 2 CH• + H• ∆H° = 395 kJ mol–1
Propane 2° Radical

CH 3 CH 2 CH 2 —H CH 3 CH 2 CH 2 • + H• ∆H° = 410 kJ mol–1
Propane 1° Radical

CH 2 =CH—H CH 2 =CH• + H• ∆H° = 452 kJ mol–1
Ethene Vinyl radical

1) An allylic C–H bond of propene is broken with greater ease than even the 3°

C–H bond of isobutene and with far greater ease than a vinylic C–H bond.

H 2 CCHCH 2 H + X H 2 CCHCH 2 + H X Eact is low

H 3 CCHCHH + X H 3 CCHCH+ H X Eact is high