N
X
C
O
N
S
Hal
Solvents
Natural
Products
P Si
C
C
C C
C
C
308
7 IR
Assignment
Range
Comments
CH 3 δ as
1470–1430
Medium, coincides with CH 2 δ
Beyond normal range:
1440–1400
CH 3 –C=O, methyl ketones, acetals, CH 3 –C=C
CH 2 δ
1475–1450
Medium, coincides with CH 3 δ as
Beyond normal range:
≈1440
CH 2 –C=C
CH 2 –C– – – C
≈1425
CH 2 –C=O, CH 2 – C– – – N,
CH 2 –X (X: hal, NO 2 , S, P)
CH 3 δ sy
1395–1365
Medium. Doublet in compounds with geminal
methyl groups:
≈1385, ≈1370
CH(CH 3 ) 2 , of equal intensity (γ: 1175–1140, d)
≈1385, ≈1365
C(CH 3 ) 2 , 1385 weaker than 1365 (γ: 1220–
1190, often d)
≈1390, ≈1365
C(CH 3 ) 3 , of equal intensity, sometimes triplet
(γ: 1250–1200, d)
N(CH 3 ) 2 , no doublet
Solid-state spectra: sometimes doublet also in
the absence of geminal methyl groups
Beyond normal range:
1325–1310
SO 2 –CH 3
1330–1290
S–CH 3 , sulfides
1310–1280
P–CH 3
1275–1260
Si–CH 3 , strong, sharp
CH 3 γ
1250–800
Intensity variable, of no practical significance.
Strong band in compounds with geminal
methyl groups:
1175–1140
CH(CH 3 ) 2 , doublet
1220–1190
C(CH 3 ) 2 , generally doublet
1250–1200
C(CH 3 ) 3 , doublet, often not resolved
Beyond normal range:
≈765
SiCH 3
≈855, ≈800
Si(CH 3 ) 2
≈840, ≈765
Si(CH 3 ) 3