Nonene, fragmentation

In Table 22 the probabilities for losing a given position to the neutral lost from heptene- or nonene-fragment ions of alkanes are compared with the corresponding probabilities for 1-heptene and 1-nonene. The data were obtained from 38 (25) selected 10 (Cii)-Ci6 alkanes, labelled in such a manner that the heptene (nonene) fragment ion had the label(s) in a predictable position [beside a possible small contribution by a... 

The reactions of 1,3-dihaloadamantanes with various carbanions in DMSO have been studied.18 For example, potassium enolates of acetophenone and pinacolone and the anion of nitromethane react with 1,3-diiodoadamantane (19) under photo-stimulation a free-radical chain process forms a 1-iodo monosubstitution product (20) as an intermediate, which undergoes concerted fragmentation to yield derivatives of 7-methylidenebicyclo[3.3.1]nonene (21). These and other results were interpreted in terms of the Srn1 mechanism. The work has been extended to the reactions of 1- and 2-halo- and 1,2-dichloro-adamantanes, examples of the SrnI mechanism again being found.19... 

Photostimulated, S r k 1 reactions of carbanion nucleophiles in DMSO have been used to advantage in C—C bond formation (Scheme 1).25-27 Thus, good yields of substitution products have been obtained from neopentyl iodide on reaction with enolates of acetophenone and anthrone, but not with the conjugate base of acetone or nitromethane (unless used in conjunction, whereby the former acts as an entrainment agent).25 1,3-Diiodoadamantane forms an intermediate 1-iodo mono substitution product on reaction with potassium enolates of acetophenone and pinacolone and with the anion of nitromethane subsequent fragmentation of the intermediate gives derivatives of 7-methylidenebicyclo[3.3.1]nonene. Reactions of 1,3-dibromo- and 1-bromo-3-chloro-adamantane are less effective.26... 

Figure 8.3 Mass spectra of an NPEO mixture with an average EO number of four acquired by (a) ESI, and (b) APCI. In the electrospray spectrum, sodiated molecules are observed. In the APCI, various ions ate observed protonated molecules ( ), ammoniated molecules ( ), and fragments due to the loss of nonene from the protonated molecule (A) (Reprinted from [28] with permission, 2001, Wiley Sons Ltd.).

In positive-ion APCI, either protonated or ammoniated molecules are observed, and fragments due to the loss of nonene. Low-mass NPEO suffer from enhanced background noise [30]. For quantitative analysis, electrospray LC-MS is preferred, while the protonated molecules generated in APCI can be readily fragmented in MS-MS for structure elucidation [28]. The positive ESI and APCI mass spectra of an NPEO with an average EO number of four are shown in Figure 8.3. 

Preparation of the lactone fragment started with a mixture of (2 ,45) and (25,4S)-4-methyl-2-phenylsulfenyl-y-butyrolactone (53) which was alkylated with ( )-l,9-diiodo-l-nonene. The corresponding iodo compound 100 so obtained was then coupled with the alkyne 99 through the efficient palladium catalyzed reaction (Pd(PPh3)4, Cul, Et3N, room temperature) in 86 % yield. Enyne reduction of 101 with Wilkinson s catalyst, then oxidation of the sulfide into sulfoxide and subsequent thermal elimination gave rise to the title compound 90. The synthesis was achieved in 20 steps and in 0.36 % yield. 

The purified dihydroxy acid was a labile component and decomposed during heating into carbonyls and oxoacids. Figure 8 presents some results of the thermal fragmentation at pH 4 - 5 in a Likens-Nickerson distillation. It can be seen that we characterized constituents similar to those in the linoleate experiment of cucumber homogenates. 50 mg precursor (9,10-dihydroxy- ( Z) -1, 2-octadecenoic acid) were decomposed into 1.95 mg ( )-3-nonenal, 0.25 mg ( )-2-nonenal, 0.51 mg 2-pentylfuran, and C -oxo- and Cg-dicarboxylic acids. In our opinion this is the most important reaction in oxidized beer (producing cardboard flavor). In an analogous reaction linolenic acid was trans-... 

Recently it has been reported that oxidative cleavage of alkenes with catalytic osmium tetroxide is possible in the absence of water using the co-oxidant Oxone (KHSOs). In this case the diol is not formed and the intermediate osmate ester is oxidized by the Oxone and fragments to regenerate osmium tetroxide and release the carbonyl products. For example, the alkene 1-nonene gave octanoic acid (90% yield) under these conditions. 

In the Conia-ene reaction, a carbonyl compound enolizes and then undergoes an intramolecular ene reaction. The enol fragment serves as the ene component of the reaction, while the olefin fragment serves as the enophile. An example is the reaction of 8-methyl-7-nonen-2-one (92), which yields 2-isopropylcyclopentyl methyl ketone (93, equation 11.41). ... 

As shown in Fig. 3, the initial products from the 9- and 13-hydroperoxides of linoleic acid are the volatile aldehydes c/j-3-nonenal and hexanal and the corresponding C9 and C12 0x0 acid fragments. Analagous volatile products from linolenic acid are cw-3,c/s-6-nonadienal and cw-3-hexenal. However, in most plants, an isomerase enzyme converts the cis-3-enals to the trans-2 isomers (see Fig. 3). Such an enzyme cis-Z, trans-l-emA isomerase has been partially purified from cucumber fruits (Phillips et al., 1979). 

The lipids that constitute the cell membrane, especially those lipids containing unsaturated double bonds, are susceptible to free radical attack, leading to the formation of lipid peroxides and aldehydes (Kako 1985). A number of short chain fragments produced from peroxidation of polyunsaturated fatty acids as 4-hydroxyperoxy nonenal and 4-hydroxy 2-alkenals react with sulphydryl groups of various enzymes modifying their activities. 

One well studied system is that of the serum low density lipoprotein (LDL sections 5.3.5(e) and 5.5.3). When the lipids of this lipoprotein are peroxidized, the apoprotein becomes fragmented and there is cross-linking and residue modification. Two products of lipid oxidation, malonaldehyde and 4-hydroxy nonenal, are responsible, the latter reacting with lysines of apoprotein-B by an addition reaction. As a result LDL no longer binds to the fibroblast receptor (section 5.5.3) and has an extended half-life in blood. 

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