Double bond position

Acylation of the vinylogous pyrrolidine amide of dimedone with acetic anhydride or acetyl chloride led (possibly indirectly) to the carbon acylation product, whereas trichloroacetyl chloride gave rise to products derived from attack of chloride at the oxygenated double bond position in an initial 0-acylation product (401-404). 

In order to avoid as far as possible double bond positional isomers, a problem quite common in drugs with indene moieties, N-trityl-2-hydroxymethylmorpholine (23) was reacted with the potassium. salt of 4-hydroxy-1-indanone (24) in DMSO solvent to give condensation product 25 in good yield. Reduction of 25 with LLAIH produced the hydroxyindane which was dehydrated and deprotected with HCl to give indeloxazine (26) [8]. 

Pyrrolidine derivative of monounsaturated methyl or ethyl ester for determining the double bond position. 

For maximum selectivity, low temperatures are essential under such conditions, simple alcohols, even allylic, are unaffected, and with unsaturated lactones as substrates, the double-bond position stays unchanged. 

Either double bond position (43) or (44) is satisfactory but only (44) leads to an easy disconnection,... 

On the other hand, in order to preserve the cold properties of the fuel (Cloud Point, Pour Point and low-temperature filterability), it is mandatory not to increase the melting point, that in turn depends on both the saturated compound (stearic acid, C18 0) content and the extent of cis/trans and positional isomerization as the difference in melting point between the cis and trans isomer is at least 15°C according to double bond position as shown in Table 1. 

Monounsaturated fatty acid influence of double bond position ... 

Polyene Cyclization. Perhaps the most synthetically useful of the carbo-cation alkylation reactions is the cyclization of polyenes having two or more double bonds positioned in such a way that successive bond-forming steps can occur. This process, called polyene cyclization, has proven to be an effective way of making polycyclic compounds containing six-membered and, in some cases, five-membered rings. The reaction proceeds through an electrophilic attack and requires that the double bonds that participate in the cyclization be properly positioned. For example, compound 1 is converted quantitatively to 2 on treatment with formic acid. The reaction is initiated by protonation and ionization of the allylic alcohol and is terminated by nucleophilic capture of the cyclized secondary carbocation. 

Rando and von E. Doering have investigated the synthetic utility of double bond positional isomerization in the photolysis of a,j8-unsaturated esters,<106)... 

Double bond position, counting from the functional group... 

Fig. 3A,B Double-bond positions of monoenyl components in Type I pheromones A counting from the functional group B counting from the terminal methyl group. See text for components with an odd numbered chain (C13, C15, and C17)...

When a sufficient amount of sample is available (ca. 1 pg), monoenyl compounds can be analyzed by micro-ozonolysis with and without a solvent [146, 165]. Ozonides, directly injected into GC-MS, are reductively decomposed into two aldehydes by heat. Besides this chemical reaction, the double-bond position is easily and high-sensitively confirmed by making an adduct with DMDS, which... 

Fig. 9A,B GC-MS analysis of the pheromone extract of Anadevidia peponis (Noctuidae, 1 FE) treated with DMDS A TIC B mass chromatograms [141]. The mass chromatograms, which are multiplied by indicated factors, monitor the M+ of DMDS adducts derived from C10 to C16 monoenyl acetates (m/z 292,320,348, and 376) and some diagnostic fragment ions (m/z 89,117,145,173,175,203,231, and 259) to determine their double-bond position. Peaks I-VI indicate the DMDS adducts of the following components in the pheromone gland Z5-10 OAc (I),Z5-12 OAc (II),Z7-12 OAc (III), ll-12 OAc (IV),Z9-14 OAc (V), and Zll-16 OAc (VI)...

Abbreviations for pheromone molecules follows the following format example (Z)-7-do-decen-l-yl acetate is shortened to Z7-12 OAc where Z denotes the double bond configuration, 7 the double bond position, 12 the number of carbons in the chain OAc indicates the functional group as an acetate ester. 

Figure 1.48 Cytosine bases are susceptible to bromination at the C-5 double bond position, resulting in active intermediates capable of reacting with amine nucleophiles.

In favorable cases for some single olefmic species, thermodynamic equilibria with respect to double-bond position can be attained at low temperatures without significant oligomerization. For example, ris-2-bu-tene has been isomerized with the P(CH3)3-modified catalyst at -20°C to give the thermodynamic equilibrium mixture having the composition 78.8% trarts-2-butene, 19.5% m-2-butene, and 1.7% 1-butene. The isomerization of 4-methyl-1-pentene (or of 2-methyl-1-pentene) in the presence of the same catalyst at 0°C also leads to the thermodynamic equilibrium mixture with the composition shown in Table II. If the reaction is carried out at low temperature, the individual isomerization steps can be followed At -58°C, isomerization to ci i-4-methyl-2-pentene occurs and is followed by isomerization to the trans isomer this is then con-... 

A very important point to remember when using ozonolysis for structural investigation of polyenes is that the transoid bond is attacked preferentially34. Hence, the advantage of the ozonolysis in polymeric matter is obvious the fragments formed are easier to analyse and they are also indicative of the double-bond positions (see Schemes 1 and 2). 

Table 11.2 Systematic and common names of unsaturated fatty acids together with the shorthand designation and typical occurrence (compiled from Gunstone et al., 1994 Hilditch and Williams, 1964 Perkins, 1993 Robinson, 1982). The shorthand designation denotes Cx n where x is the number of carbon atoms and n is the number of double bonds (position of the last double bond in relation to terminal methyl group).

The results of the chemical characterization of the preorbital secretions of these dwarf antelope are summarized in Table 9 [140]. Due to the large number of double-bond positional isomers in the secretions of some of the members of the tribe, it is impossible to include all the relevant information in the table. 

Pepe, C. Sayer, H. Dagaut, J. Couffig-nal, R. Determination of Double Bond Positions in Triunsaturated Compounds by Means of Gas Chromatography/Mass Spectrometry of Dimethyl Disulfide Derivatives. Rapid Commun. Mass Spectrom. 1997, 77,919-921. 

Example The oxidative addition of dimethyl disulfide (DMDS) transforms the double bond to its 1,2-bis-thiomethyl derivative (a). Induced by charge localization at either sulfur atom, the molecular ions of DMDS adducts are prone to a-cleavage at the former double bond position (b). This gives rise to sulfonium ions that are readily identified from the mass spectrum (Chap. 6.2.5). The method can be extended to dienes, trienes, and alkynes. [70,71] (For the mass spectral fragmentation of thioethers cf. Chap. 6.12.4). 

Buser, H.-R. Am, H. Guerin, P. Rauscher, S. Determination of Double Bond Position in Mono-Unsaturated Acetates by Mass Spectrometry of Dimethyl Disulfide Adducts. Anal. Chem. 1983, 55, 818-822. 

Cyclic olefins and diolefins form much more aerosol than 1-alkenes that have the same number of carbon atoms (for example, cyclohexene 1-hexene, and 1,7-octadiene 1-octene). The same effect of chain length and double-bond position is observed for diolefins (1,7-octadiene > 1,6-heptadiene > 1,5-hexadiene, and 1,7-octadiene 2,6-octadiene). Heavier unsaturated cyclic compounds, such as indene and terpenes, form even more aerosol. 

Double bond position, counting from the functional group length 3 g g 9 10 11 12 13 14 15 16 17... 

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