¹³C-NMR SPECTROSCOPY OF FATTY ACIDS AND DERIVATIVES

Oxo (Keto) Acids

Table 1 lists chemical shifts (ppm) for several oxo (keto) acids. Many of the compounds contain a second functional group (double bond, hydroxy, chloro, azido, epoxy, or oxo). The oxo group is easily recognised by its very high chemical shift (~210 ppm) and by its strong influence on nearby carbon atoms. These are listed in Table 2 and compared with the effects of other functional groups. For practical reasons, it is necessary to split Table 1 into convenient parts.


Table 1. Chemical shifts (ppm) for a range of oxo acids and methyl esters.
Key:	1	methyl 9-oxo 18:0 (Gunstone/Tulloch)
	2	methyl 10-oxo 18:0 (Kuo)
	3	methyl 9-oxo-12c-18:1 (Lie Ken Jie, 1995, original figures to three decimal places)
	4	methyl 12-oxo 9c-18:1 (Lie Ken Jie, 1995, original figures to three decimal places)
	5	methyl 9-oxo 10t12c-18:2 (Kuklev)
	6	methyl 13-oxo 9c11t-18;2 (Kuklev)
	7	methyl 12-hydroxy-9-oxo 18:0 (Lie Ken Jie, 1996)
	8	methyl 9-hydroxy-12-oxo 18:0 (Lie Ken Jie, 1996)
	9	7-hydroxy-16-oxo-9c-18:1 acid (Lanser)
	10	methyl 7-hydroxy-17-oxo-9c-18:1 (Lanser)
	11	methyl 12-chloro-9-oxo 18:0 (Lie Ken Jie, 1996)
	12	methyl 12-azido-9-oxo 18:0 (Lie Ken Jie, 1996)
	13	methyl 9,12-dioxo 18:0 (Lie Ken Jie,1996)
	14	methyl 9,12-dioxo-10c-18:1 (Lie Ken Jie,1997)
	15	methyl 9,12-dioxo-10t-18:1 (Lie Ken Jie, 1997
	16	methyl cis-10,11-epoxy-9,12-dioxo 18:0 (Lie Ken Jie, 1997)
	17	methyl trans-10,11-epoxy-9,12-dioxo 18:0 (Lie Ken Jie, 1997)

	1	2	3	4	5	6	7	8	9	10


1	173.93	174.21	174.26	174.29	174.2	173.2	174.30	174.23	178.9	174.2
2	34.01	34.02	34.06	34.08	34.1	34.1	34.08	34.08	35.4	34.0
3	24.88	24.85	24.88	24.93	(24.9)	(24.9)	24.90	24.92	24.7	24.9
4	28.93								29.4	29.1
5	29.01								25.3	25.4
6	29.05								36.5	36.6
7	23.77		23.71		(24.1)		23.88	25.62	71.3	71.3
8	42.66	23.77#	42.68	27.48	(41.1)		42.88		35.4	35.4
9	211.03	42.70*	210.80	133.54	201.1	136.9	212.28	71.29	125.3	125.1
10	42.78	210.56	42.86	121.54	127.0	127.0	39.13	31.04	133.2	133.4
11	23.89	42.78*	21.73	41.66	142.4	142.4	31.60	39.11	27.2	27.3
12	29.21	23.84#	127.78	209.30	129.4	129.4	71.40	212.04	29.0	29.4
13	29.40		131.23	42.38	136.9	202.1	37.79	42.96	28.6	29.0
14	29.40		27.16	23.80		41.1	25.66	23.95	23.7	29.0
15	29.25					(24.1)			42.3	23.7
16	31.80	31.76	31.52	31.61			31.83	31.64	212.1	43.7
17	22.62	22.57	22.58	22.51	22.5	22.5	22.61	22.48	35.9	209.3
18	14.05	14.00	14.08	14.04	13.9	13.8	14.09	14.03	7.8	29.9

	11	12	13	14	15	16	17


1	174.12	174.25	174.17	174.30	174.21	174.25	174.37
2	34.02	34.04	34.08	34.03	34.01	34.03	34.02
3	24.92	24.88	24.92	24.87	24.84	24.86	24.81
4
5
6
7	23.84	23.76	23.78*	23.39*	23.62*	22.68*	22.87*
8	42.96	42.95	42.85	42.45#	41.54#	41.03#	37.25
9	209.98	210.21	209.60	203.15$	200.71$	204.75	204.73#
10	39.41	38.90	36.03	135.57£	136.23£	55.51£	57.50
11	32.06	28.94	36.03	135.81£	136.30£	58.56£	57.50
12	63.58	62.36	209.60	203.18$	200.82$	204.75	204.79#
13	38.84	34.53	42.85	42.58#	41.64#	41.18#	37.37
14	26.06	26.04	23.89*	23.48*	23.71*	22.78*	22.96*
15
16	31.69	31.69	31.64	31.59	31.55	31.51	31.49
17	22.59	22.57	22.54	22.48	22.47	22.46	22.44
18	14.03	14.03	14.03	14.04	14.02	14.02	14.01

* # £ $ these pairs of numbers can be interchanged.
Values in brackets were assigned or corrected in assembling this table.
Some reports include chemical shifts for unassigned signals but are not reported here.

	α	β	γ	δ	other

Table 2. Effect of various functional groups on nearby carbon atoms which usually have a chemical shifts of ~ 29.7 ppm.

Cis double bond	-2.5	0	-0.4	-0.2
Trans double bond	+2.9	-0.1	-0.5	-0.2
Hydroxy	+7.8	-4.0	+0.06	-0.06	-0.09, -0.05
Acetoxy	+4.4	-4.4	-0.20	-0.20	-0.10, -0.05
Oxo (keto)	+13.10	-5.75	-0.40	-0.25	-0.20, -0.08
Cis epoxy	+1.71	-2.93	-0.38
Trans epoxy	+2.57	-3.50	-0.23

References

Gunstone, F.D. High resolution of ¹³C-NMR spectroscopy of lipids. pp. 1-68. In: Advances in Lipid Methodology - Two (ed. W.W. Christie, Oily Press, Dundee) (1993).
Kuklev, D.V., Christie, W.W., Durand, T., Rossi, J.C., Vidal, J.P., Kasyanov, S.P., Akulin, V.N. and Bezuglov, V.V. Synthesis of keto- and hydroxydienoic compounds from linoleic acid. Chem. Phys. Lipids, 85, 125-134 (1997).
Lanser, A.C. Bioconversion of oleic acid to a series of keto-hydroxy and dihydroxy acids by Bacillus species NRRL BD-447: Identification of 7-hydroxy-16-oxo-9-cis-octadecenoic acid. J. Am. Oil Chem. Soc., 75, 1809-1813 (1998).
Lanser, A.C. and Manthey, L.K. Bioconversion of oleic acid by Bacillus species NRRL BD-447: Identification of 7-hydroxy-17-oxo-9-cis-octadecenoic acid. J. Am. Oil Chem. Soc., 76, 1023-1026 (1999).
Lie Ken Jie, M.S.F. and Cheng, K.L. Nuclear magnetic resonance spectroscopic analysis of homoallylic and bis homoallylic substituted methyl fatty ester derivatives. Lipids, 30, 115-120 (1995).
Lie Ken Jie, M.S.F. and Lam, C.K. Regiospecific oxidation of unsaturated fatty esters with palladium (II) chloride/p-benzoquinone: a sonochemical approach. Chem. Phys. Lipids, 81, 55-61 (1996).
Lie Ken Jie, M.S.F., Pasha, M.K. and Lam, C.K. Ultrasonically stimulated oxidation reactions of 2,5-disubstituted C₁₈ furanoid fatty ester. Chem. Phys. Lipids, 85, 101-106 (1997).
Kuo, T.M., Lanser, A.C., Kaneshiro, T. and Hou,C.T. Conversion of oleic acid to 10-ketostearic acid by Sphingobacterium sp. strain O22. J. Am. Oil Chem. Soc., 76, 709-712 (1999).

The Scottish Crop Research Institute (MRS Lipid Analysis), Invergowrie, Dundee (DD2 5DA), Scotland

Lipid Library

The Lipid Library

13C-NMR SPECTROSCOPY OF FATTY ACIDS AND DERIVATIVES

Oxo (Keto) Acids

Table 1. Chemical shifts (ppm) for a range of oxo acids and methyl esters.

Table 2. Effect of various functional groups on nearby carbon atoms which usually have a chemical shifts of ~ 29.7 ppm.

References

¹³C-NMR SPECTROSCOPY OF FATTY ACIDS AND DERIVATIVES