Instant Notes: Analytical Chemistry

258 Section E – Spectrometric techniques

nA

dA

nX

nA

dX

nX

dA dX

JAX JAX JAXJAX JAX

Orientations

of

X spin A spin

Area ratio

1:1

(a) –CH–CH–

Methines

(AX)

Orientations

of

X spins A spin

Area ratio

1:2

12 :: 1

(b) –CH–CH 2 –

Methine/methylene

(AX 2 )

Orientations

of

X spins A spins

Area ratio

2:3

Orientations

of

X spins A spins

Area ratio

1:1

nA

dA

JAXJAX

12 :: 1

nX nA

dX

JAXJAX

12 :: 1

nX

dX

JAXJAX

12 :: 1

dA

JAXJAXJAX

13 ::: 31

(c) –CH 2 –CH 2 – (A 2 X 2 )

Methylenes

(d) –CH 2 –CH 3 (A 2 X 3 )

Ethyl

Orientations

of

A spin

Area ratio

1:6

nA nX

JAXJAXJAXJAXJAXJAX JAX

dA dX

(e) –CH–(CH 3 ) 2 (AX 6 )

Isopropyl

Orientations omitted

for clarity

Fig. 8. Diagrammatic representations of first order proton-splitting patterns for two coupled groups.