Advices For Studying Organic Chemistry

(2)

C–H bond C–D bond

ν = 4.12 Kμ^ ν = 4.12 Kμ^

K= 5 x 10^5 dynes/cm K= 5 x 10^5 dynes/cm

μ =

C H

C H

M M

M M

+ = 12 1

( 12 )( 1 )

+ = 0.923 μ = C D

C D

M M

M M

+ = 12 2

( 12 )( 2 )

+ = 1.71

ν = 4.12^5 0.923 x^10

5

= 3032 cm–1 (calculated);

ν = 3000 cm–1 (experimental)

ν = 4.12^5 x 1.71^10

5

= 2228 cm–1 (calculated);

ν = 2206 cm–1 (experimental)

(3)

CC CC CC
2150 cm–1 1650 cm–1 1200 cm–1
increasingK

CH CC CO CCl CBr CI
3000 cm–1 1200 cm–1 1100 cm–1 800 cm–1 550 cm–1 ~500 cm–1
increasing μ

(4) Hybridization affects the force constant K:
sp sp^2 sp^3

CH CH CH
3300 cm–1 3100 cm–1 2900 cm–1

(5) K increases from left to the right across the periodic table:

C–H: 3040 cm–1 F–H: 4138 cm–1

(6) Bending motions are easier than stretching motions:

C–H stretching: ~ 3000 cm–1 C–H bending: ~ 1340 cm–1