Hydroxy and Hydroperoxy Acids
Saturated Hydroxy and Acetoxy Compounds
Tulloch et al.and Maazurek  have reported NMR spectra for most of the regioisomeric hydroxy- and acetoxy-stearates. The CHOH or CHOAc group has a considerable effect on the chemical shifts of nearby carbon atoms as indicated below. These values are changes in shift from the normal value of 29.65 ppm for mid-chain CH2 groups (Table 1).
Isbell and Mund  reported the 13C-NMR spectrum of 5-hydroxyeicosanoic acid (C20) and several of its ethers.
Unsaturated Mono-hydroxy Acids
Unsaturated hydroxy acids with the structural unit -
where n = 0, 1, or 2 have been examined and the results are summarised in Table 4 below. Additional data for some diacetoxy 18:4 esters  and some aken-1-ols  can be obtained from the references given. Pfeffer et al.  concluded that the effect of the OH function on nearby olefinic carbon shifts was as follows (values for n = 0 were calculated by the compiler). The values cited are to be added to or subtracted from the chemical shifts normally associated with a double bond in the appropriate position.
|n = 0||cis||2.1 (β) and 2.9 (γ)|
|n = 0||trans||1.6 (β) and 2.9 (γ)|
|n = 1||cis||3.08 (γ) and -4.63 (δ)|
|n = 1||trans||4.06 (γ) and -4.18 (δ)|
|n = 2||cis||-0.73 (δ) and 0.73 (ε)|
Lie Ken Jie and Cheng  have provided chemical shifts (ppm) for a range of homoallylic and bis-homoallylic esters based on methyl ricinoleate (12-OH 9c-18:1) and methyl isoricinoleate (9-OH 12c-18:1) where the functional group is hydroxy, acetoxy, chloro, azido, or oxo (Table 5 below).
Chemical shifts (ppm) for a range of oxylipins (hydroxy unsaturated C20 acids and esters) are listed by Jiang and Gerwick .
Data presented by Rakoff et al.  for threo and erythro saturated and unsaturated acids are given in Table 6 below. The threo and erythro isomers are distinguishable by their NMR spectra, particularly by the chemical shifts of CH2 groups α and β to the diol unit. The chemical shifts for 7,10-dihydroxystearic acid given by Knothe et al.  have been assigned by the compiler.
Hydroperoxy and Other Oxidized Acids
Neff et al.  and Frankel et al.  have examined the NMR spectra of mono-, bis-, and tris-hydroperoxy esters produced during autoxidation of trilinolein and trilinolenin. Chemical shifts (ppm) for the carbon atoms α and β to the OOH group are given below. These, presumably, relate to the structural unit (Table 2):
Frankel et al. [13,14] have given chemical shifts for two stereoisomers of the 9-hydroperoxy 10,12-hydroperoxide (Table 3).
In a more recent study, Silwood and Grootveld  reported some 13C chemical shifts for glycerol esters containing 9-OOH 10t,12c-18:2 (86.0, 132.5, 131.0, 130.0, and 132.0 for C9-13, respectively) and 9-OOH 10t,12t-18:2 (87.5, 132.5, 133.0, 130.0, and 131.0 for C9-13, respectively) and for the aldehyde carbon atom in alkanals (201.0 ppm), 2t-alkenals (193.2 ppm), 2t,4t-alkadienals (191.5 ppm), and 2c,4t-alkadienals (192.8 ppm).
Primary Alcohols and Hydroperoxides
Bascetta and Gunstone  examined a series of primary alcohols (RCH2OH) and hydroperoxides (RCH2OOH) with 8-18 carbon atoms. Chemical shifts for the C18 compounds are listed in Table 6 below. They concluded that the influence of the CH2X group on the α (C2) and β (C3) carbon atoms is +3.34 and –3.69 for the CH2OH and –1.89 and –3.58 for the CH2OOH group relative to the CH2 group at 29.30.
Knothe et al. [15-18] have studied the allylic oxidation of olefinic alcohols, acids, and esters of varying chain length with selenium dioxide to produce a wide variety of mono- and dihydroxy olefinic compounds that can be hydrogenated to their saturated derivatives. These compounds contain the structural units -
–CH(OH)CH=CH- and -CH(OH)CH=CHCH(OH)-
- and their dihydro derivatives. A lot of 13C-NMR data have been reported but the original papers must be consulted for details. Kuklev et al.  have provided information on hydroxy dienoic acids (9- and 13-HODE).
Hou and others, studying the microbial oxidation of oleic and other unsaturated acids, have isolated and identified several unsaturated hydroxy acids for which they have reported 13C-NMR shifts. These include the following C18 acids some of which are included in Table 4:
10-hydroxy 8t-18:1 ; 10-hydroxy 12c-18:1 ; 10-hydroxy 6c,12c-18:2 ; 10-hydroxy 12c,15c-18:2 ; 7-hydroxy-17-oxo 9c-18:1 ; 7-hydroxy-16-oxo 9c-18:1 ; 7,10-dihydroxy 8t-18:1 ; 7,10-dihydroxy 18:0 ; 7,10,12-trihydroxy 8t-18:1 ; 12,13,17-trihydroxy 9c-18:1 , 12,13-dihydroxy 10t-18:1 , and the acetylenic compounds 8-hydroxy 9a,11t-18:2 and 8,11-dihydroxy 9a-18:1 .
Tables 4 to 6
|Table 4. Chemical shifts (ppm) for unsaturated hydroxy acids containing the structural unit
-CH2CH2CH(OH)(CH2)nCH=CHCH2- where n = 0, 1, or 2.
|9-OH 10c||0||37.6||67.8||-||-||132.1, 132.8||27.6||3|
|12-OH 10c||0||37.6||67.5||-||-||131.9, 132.8||27.7||3|
|12-OH 9c||1||25.8||37.0||71.6||35.5||-||133.0, 125.5||27.4||4|
|10-OH 12c||1||36.6||71.2||35.2||-||125.1, 132.9||27.2||5|
|10-OH 12c,15c||1||36.7||71.2||35.2||-||131.9, 125.4||24.7a||5|
|9-OH 12c||2||25.50||37.36||71.71||37.46||23.60||129.19, 130.69||27.23||6|
|10-OH 6c||2||25.64||37.22||71.43||37.54||23.53||129.65, 129.85||26.75||6|
|9-OH 5c||2||25.70||37.24||71.51||37.75||23.55||129.09, 130.55||26.56||6|
|9-OH 10t||0||37.4||73.2||-||-||132.1, 133.2||32.1||3|
|12-OH 10t||0||37.4||73.1||-||-||131.9, 133.3||32.2||3|
|12-OH 9t||1||25.7||36.9||71.2||40.9||-||134.4, 126.2||32.7||4|
a = 126.7 (C15) 130.9 (C16).
These assignments are listed so that the CH(OH) and CH=CH chemical shifts lie in the same vertical column. CH2 groups between these two are absent when there is a. Other carbon atoms can be identified from these fixed points. For example in the entry for 12-OH 9c the shifts given relate to C14 to C8. Some of these values may also be influenced by acid/ester or methyl end groups. The compiler of this information has made or adjusted some of the assignments.
|Table 5. Chemical shifts (ppm) for methyl ricinoleate (12-OH 9c-18:1) and isoricinoleate (9-OH 12c-18:1) [9a]|
a = unassigned values between 28.829 and 29.463.
Information is also given in the original paper for derivatives of these two esters in which the OH group is replaced by N3, OAc, Cl, and oxo functions.
|Table 6. Chemical shifts (ppm) for selected hydroxy and hydroperoxy C18 compounds|
|where||1||methyl erythro-9,10-dihydroxystearate |
|2||methyl threo-9,10-dihydroxystearate |
|3||methyl threo-12,13-dihydroxy-cis-9-octadecenoate |
|4||methyl threo-12,13-dihydroxy-trans-9-octadecenoate |
|5||7,10-dihydroxystearic acid |
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Updated January 27, 2007