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, 1993)
  2 methyl 10-oxo 18:0 (Kuo et al., 1999)
  3 methyl 9-oxo-12c-18:1 (Lie Ken Jie and Cheng, 1995, original figures to three decimal places)
  4 methyl 12-oxo 9c-18:1 (Lie Ken Jie and Cheng, 1995, original figures to three decimal places)
  5 methyl 9-oxo 10t,12c-18:2 (Kuklev et al., 1997)
  6 methyl 13-oxo 9c,11t-18;2 (Kuklev et al., 1997)
  7 methyl 12-hydroxy-9-oxo 18:0 (Lie Ken Jie and Lam, 1996)
  8 methyl 9-hydroxy-12-oxo 18:0 (Lie Ken Jieand Lam, 1996)
  9 7-hydroxy-16-oxo-9c-18:1 acid (Lanser, 1998)
  10 methyl 7-hydroxy-17-oxo-9c-18:1 (Lanser, 1998)
  11 methyl 12-chloro-9-oxo 18:0 (Lie Ken Jie and Lam, 1996)
  12 methyl 12-azido-9-oxo 18:0 (Lie Ken Jie and Lam, 1996)
  13 methyl 9,12-dioxo 18:0 (Lie Ken Jie and Lam,1996)
  14 methyl 9,12-dioxo-10c-18:1 (Lie Ken Jie et al., 1997)
  15 methyl 9,12-dioxo-10t-18:1 (Lie Ken Jie et al., 1997)
  16 methyl cis-10,11-epoxy-9,12-dioxo 18:0 (Lie Ken Jie et al., 1997)
  17 methyl trans-10,11-epoxy-9,12-dioxo 18:0 (Lie Ken Jie et al., 1997)
 12345678910
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
 11121314151617
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 parentheses were assigned or corrected in assembling this table.
Some reports include chemical shifts for unassigned signals but are not reported here.
Table 2. Effect of various functional groups on nearby carbon atoms, which usually have a chemical shifts of ~ 29.7 ppm
 αβγδOther
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 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).
  • 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).
  • 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).