Benzaldehyde abnormal deuterium distribution

However, abnormal deuterium distribution does not always result from adulteration or unknown sources. It is known that auto-oxidation of benzaldehyde will enrich the deuterimn distribution on the formyl site of tlie remaining benzaldehyde (4,5). Therefore, old samples may have a higher molar fraction of deuterium at position 1. This same reaction does not affect the isotope distribution on the aromatic moiety. 

Recently, we also observed abnormal deuterium distribution of a sample of benzaldehyde, which deviated significantly from the expected cluster formed by benzaldehydes produced from cinnamic aldehyde. Adulteration and use of a starting material from an unknown source were ruled out. Experiment results indicated that the deuterium shift was not due to oxidation and isotope exchange. No chromatography process was used. Our attention focused on tlie distillation process. 

Figure 4, PCA plot of abnormal deuterium distribution of benzaldehyde...

SNIF-NMR is a powerful method for the authentication analysis of benzaldehyde products. However, manufacturing processes may cause the deuterium to shift on the carbonyl site. In some cases, the current SNIF NMR method cannot differentiate abnormal distribution of deuterium caused by adulteration or by production processes that lead to false negative or false positive conclusions of a product. Deuterium on the aromatic sites of benzaldehyde is more stable and is not affected by the known manufacturing processes. The aromatic deuterium distribution is very specific and can be used to classify benzaldehyde products from fossil or different botanical origins. The proposed improvement needs to be further developed and validated. 

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See also in sourсe #XX -- [ , , ]

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