Double bonds detection

Irreversible complex forma- [21] tion or saturation of double bonds detection by IR... 

Measurement of Unsaturation. The presence of double bonds in a fatty acid side chain can be detected chemically or through use of instmmentation. Iodine value (IV) (74) is a measure of extent of the reaction of iodine with double bonds the higher the IV, the more unsaturated the oil. IV may also be calculated from fatty acid composition. The cis—trans configuration of double bonds may be deterrnined by infrared (59) or nmr spectroscopy. Naturally occurring oils have methylene-intermpted double bonds that do not absorb in the uv however, conjugated dienes maybe deterrnined in an appropriate solvent at 233 nm. 

Diazirines (3) smoothly add Grignard compounds to the N—N double bond, giving 1-alkyldiaziridines. Reported yields are between 60 and 95% without optimization (B-67MI50800). The reaction is easily carried out on a preparative scale without isolation of the hazardous diazirines and may serve as an easy access to alkylhydrazines. The reaction was also used routinely to detect diazirines in mixtures. The diaziridines formed are easily detected by their reaction with iodide. Phenyllithium or ethylzinc iodide also add to (3) with diaziridine formation. 

II. Structure, Preparation, and Detection of Iminium Salts A. Structure oe Iminium Salts The positively charged carbon-nitrogen double bond... 

As far as oxidation of the polymer with oxygen of the air is concerned, the /3-hydrogen atom in the neighborhood of the C=C double bond is the most likely one to be attacked by oxygen with the formation of hydroperoxide which undergoes further decomposition [19]. OH and CO groups have been detected spectroscopically in the polymer [67,83]. 

Pseudo-/ -DL-gi Zopyranose triacetate (36) was prepared by hydroxyla-tion of the enetriol triacetate (32) and converted to the corresponding pentol and pentaacetate. The intermediate 32 was obtained by Diels-Alder reaction (200°C., two days) of rans/ rans-l,4-diacetoxy-l,3-buta-diene with allyl acetate. The double bond was surprisingly inert to the usual additive reagents and not detectable by infrared spectroscopy because of near-symmetry, but it did react with tert-butyl hydroxperoxide to give 36 in about 30% yield (27). 

For product 1 (X = Y = H) an equilibrium between the two possible double-bond isomers has been detected by NMR spectroscopy. For the dibromo derivative (X = Y = Br) a tub conformation has been determined by X-ray structural analysis. 

A )-1-Methyl-2-butenylstannanes similarly give ann-homoallylic alcohols on healing with aldehydes, only traces of the sjn-isomers being detected. Moreover, these reactions are highly stereoselective for formation of (Z) double bonds in the products. It would appear that small amounts (ca. 10%) of the (Z)-isomers in the (A)-l-methyl-2-butenylstannanes (see Section 1.3.3.3.6.1.1.2.) do not interfere because they are significantly less reactive17. 

First consider the interaction of radicals with monomers. Some behave as described in the classic texts and give tail addition as the only detectable pathway (Scheme 3.3). However, tail addition to the double bond is only one of the pathways whereby a radical may react with a monomer. The outcome of the reaction is critically dependent on the structure of both radical and monomer. 

Other evidence cited for SET mechanisms has been detection of radical or radical ion intermediates by ESR or CIDNP the finding that such reactions can take place at 1 -norbomyl bridgeheads and the formation of cyclic side products when the substrate has a double bond in the 5,6 position (such substrates are called radical probes). 

When double bonds are reduced by lithium in ammonia or amines, the mechanism is similar to that of the Birch reduction (15-14). ° The reduction with trifluoro-acetic acid and EtsSiH has an ionic mechanism, with H coming in from the acid and H from the silane. In accord with this mechanism, the reaction can be applied only to those alkenes that when protonated can form a tertiary carbocation or one stabilized in some other way (e.g., by a OR substitution). It has been shown, by the detection of CIDNP, that reduction of a-methylstyrene by hydridopenta-carbonylmanganese(I) HMn(CO)5 involves free-radical addition. ... 

The reaction with bromine is very rapid and is easily carried out at room temperature, although the reaction is reversible under some conditions. In the case of bromine, an alkene-Br2 complex has been detected in at least one case. Bromine is often used as a test, qualitative or quantitative, for unsaturation. The vast majority of double bonds can be successfully brominated. Even when aldehyde, ketone, amine, so on functions are present in the molecule, they do not interfere, since the reaction with double bonds is faster. 

Hydrogenation catalysts,such as platinum, palladium, nickel, and so on. In this case the reaction is the reverse of double-bond hydrogenation (15-11 and 15-15), and presumably the mechanism is also the reverse, though not much is known. Cyclohexene has been detected as an intermediate in the... 

For instance morphine (1) can be detected by the formation of various quinones via apomorphine as intermediate [4, 12, 13]. All morphines with an OH group in the 6-position and a double bond (codeine, ethylmorphine etc.) first undergo an acid-catalyzed rearrangement according to the following scheme [12] ... 

The well-known triphenyltetrazolium chloride (TTC) reaction for the detection of a-ketolsteroids, pyridinium carbinols and pyridinium glycols can also be included here [20-23]. The chromophore system of the red-colored formazan dye produced by reduction of the TTC is composed of highly conjugated double bonds resulting from the combination of a phenylhydrazone group with an azo group ... 

Elimination of vinyl groups, [14] addition of iodine to double bonds, ester cleavage detection by IR... 

Note It is occasionally recommended that sodium acetate be added to the reagent [2]. Thiophosphate insecticides with a simple P—S bond yield yellow chromatogram zones and those with a P=S double bond yield brown ones on a light brown background [10]. Further treatment of the stained chromatogram with iodine vapors increases the detection sensitivity [7] more than does spraying afterwards with caustic soda solution, which is also occasionally recommended [16, 17, 20, 21]. 

The detection limits for compounds with P=S double bonds are lower than those for substances with single P—S bonds [7]. They are lower on silica gel than on polyamide layers [15] and are, for instance, 10-20 ng substance per chromatogram zone for... 

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