DMDS derivatization

DMDS derivatization was extended to diunsaturated fatty compounds by Vin-centi et al. (27). Only when the two double bonds in dienes are separated by at least foiu methylene groups do the expected di-adducts arise (27). When the two double... 

Dimethyl Disulfide Derivatization. Dimethyl disulfide (DMDS) derivatization was performed on the unsaturated anacardic acids in order to locate the position of the double bond (2.). A solution of the anacardic acid (0.05-0.1 mg) was dissolved in hexane (1.75mL). DMDS (2.5mL) and iodine solution (0.25mL of a 60mg la/mL ether) were added to the reaction vial, and the reaction was allowed to run overnight at 40°C. After the reaction was complete, 5mL of a 5% (w/v) solution of sodium thiosulfate was added to the reaction mixture to remove the excess iodine. The organic layer was removed, and evaporated to leave the crude DMDS derivative, which was purified by hpic, before being submitted for mass spectrometric analysis. 

Dimethyldisulfide derivatization is the most common method used for double bond position determination. Reaction of the alkene in hexane with dimethyl disulfide (DMDS) and iodine under an inert atmosphere at 60°C produces the DMDS adduct. MS fragmentation of the DMDS derivatives occurs between the methylsulfide groups, thus locating the original double bond position (Figure 7). DMDS derivatization was used for the determination of the double bond position in (E)-8-dodecenyl acetate, the sex pheromone of the citrus fruit borer. 

Figure 7 General scheme for dimethyl disulfide (DMDS) derivatization of double bonds.

Fig.8A,B Derivatization of Type I pheromones A Z7-12 OAc with dimethyl disulfide (DMDS) and mass spectra of the DMDS adduct B E5,Z7-12 OAc with 4-methyl-1,2,4-triazoline-3,5-dione (MTAD) and mass spectra of the MTAD adduct...

The location of double bonds in polyunsaturated fatty acids by GC-MS involves many different methodologies either by suitable derivatization or Cl techniques (Christie, 1996 Lopez and Grimalt, 2004 Jhama et al., 2005). Derivatization reactions include the reaction with DMOX (Fay and Richli, 1991 Dobson and Christie, 2002), dimethyl disulfide (DMDS) (Moss and Lambert-Fair, 1989), as well as methoxy and methoxybromo derivatives (Shantha and Kaimal, 1984) besides other known derivatives. Cl allows specific reactions with C,C-double... 

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