Ethylene methine

The nmr spectmm of PVAc iu carbon tetrachloride solution at 110°C shows absorptions at 4.86 5 (pentad) of the methine proton 1.78 5 (triad) of the methylene group and 1.98 5, 1.96 5, and 1.94 5, which are the resonances of the acetate methyls iu isotactic, heterotactic, and syndiotactic triads, respectively. Poly(vinyl acetate) produced by normal free-radical polymerization is completely atactic and noncrystalline. The nmr spectra of ethylene vinyl acetate copolymers have also been obtained (33). The ir spectra of the copolymers of vinyl acetate differ from that of the homopolymer depending on the identity of the comonomers and their proportion. 

Dicentrine, CgoHjjOjN. (Items 36, 37, 39, 40 list, pp. 172-3.) This alkaloid crystallises, from ether, alcohol, or ethyl acetate in prisms, m.p. 168-9° [a]i) + 62-1° (CHCI3), and yields well-crystallised salts. It contains two methoxyl groups and yields a monoacetyl derivative, colourless leaflets, m.p. 202°, which is not hydrolysed even by boiling alcoholic potash. 1 The methiodide, B. CH3I. HjO, has m.p. 224°, and according to Manske, yields a methine base, m.p. 158-9°, the methiodide of which with potassium hydroxide solution decomposes into trimethylamine and a crystalline substance, presumably a substituted phenanthrenyl-ethylene, which polymerises on recrystallisation. 

FIGURE 13.3 Mechanism of (multiple) grafting of maleic anhydride onto methine and methylene units of ethylene-propylene copol3mier (EPM). 

Methine-containing dye classes, 9 503-504 Methine groups, ethylene oxide reaction with, 10 639... 

We considered the polymer chain could be formed by either primary or secondary insertion. Primary insertion is when the monomer forms a bond with the methylene group to the catalyst metal and secondary insertion is where the metal and monomer form a bond with the propylene methine group. Ethylene must always add by primary insertion, but propylene can add either way. And, in fact, the presence of the ag secondary carbon shows the presence of a two carbon methylene sequence which can occur only if both types of insertion are in force. 

Table 3. The comparison of calculated and observed chemical shifts for methylene and methine carbons in poly(ethylene-co-p-methylstyrene) and poly(ethylene-co-styrene).

Fig. 23. A part of the infra red spectra showing the carbonyl band absorption for (A) an ethylene-vinyl acetate copolymer and its blends with (B) 40 % and (Q 80% chlorinated polyethylene. The peak is shifted due to a specific interaction between the carbonyl and the methine hydrogen of chlorinated polyethylene. The shifted peaks are actually a combination of a shifted and an unshifted peak at different ratios...

On catalytic hydrogenation of methine-I only one double bond was reduced and dihydromethine-I (XV) was formed in which was retained the original ethylenic linkage 980 cm i). Hofmann degra-... 

Carbon 13 NMR spectra of low density-polyethylene and ethylene propylene copolymer were observed at a freqeuncy of 125.77 MHz. The INEPT method was applied to identify methyl, methylene, and methine carbons. 

Bovey et al.(3) also observed both H-links and Y branches in an NMR study of a normal alkane irradiated in vacuum in the molten state. The long chain Y branch was easy to recognize in the present study because of the presence of a methine resonance at 38.19 ppm, an a methylene resonance at 34.55 ppm and a P methylene resonance at 27.30 ppm. These assignments are in excellent agreement with those of Bovey et al. (3) and correspond closely to the methine and a, p methylene resonances observed for an ethylene-l-octene copolymer as shown below ... 

The ease of reaction depends both on the CH acidity of the addend and on the polarizability of the ethylenic double bond of the acceptor. Thus, in general, only such compounds function as addend in which a methylene or methine group is activated by two neighboring carbonyl or nitrile groups, as, for example, in malonic esters, malonodinitrile, cyanoacetic esters, 1,3-dioxo compounds and 3-oxo carboxylic esters, and their monoalkyl substitution products. The ethylenic double bond of the acceptor is polarized by conjugation with a polar multiple bond, so that the olefinic component is usually an unsaturated ketone, an, / -unsaturated ester, or an, / -unsaturated nitrile. The addition is catalysed by bases such as potassium hydroxide solution, sodium ethoxide, and amines. 

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