Phenylpyrazine derivative

The FT-IR technique using reflection-absorption ( RA ) and transmission spectra to quantitatively evaluate the molecular orientation in LB films is outlined. Its application to some LB films are demonstrated. In particular, the temperature dependence of the structure and molecular orientation in alternate LB films consisting of a phenylpyrazine-containing long-chain fatty acid and deuterated stearic acid (and of their barium salts) are described in relation to its pyroelectricity. Pyroelectricity of noncentrosymmetric LB films of phenylpyrazine derivatives itself is represented, too. Raman techniques applicable to structure evaluation of pyroelectric LB films are also described. 

Pyroelectricity of several kinds of alternating LB films consisting of phenylpyrazine derivatives and stearic acid was measured by the static method at various temperatures. Effects of thermal expansion and molecular packing density of the film on pyroelectricity were also examined. The following conclusions were derived. 

The simple phenyl-substituted pyrazines do undergo nitration in the phenyl ring for example, 2-phenylpyrazine yields the 4-nitrophenyl derivative (mixed acid), although 5-phenyl-2-pyrazinone forms the 3-nitropyra-zinone under similar conditions (75MI1). However, 2,5-dimethyl-3,6-diphenylpyrazine and its /V,A -dioxide are both reported to be nitrated to give the bis-(3-nitrophenyl) products (55JCS3094). 

Dichloropyrazines have also been prepared from the corresponding hydroxy compounds as follows 2,3-dihydroxypyrazine with phosphoryl chloride containing pyridine (481, 757) [see Schneller and May (828) re the use of phenylphosphonic dichloride at 150-170°] 2,3-dihydroxypyrazine and its methyl, dimethyl, phenyl, diphenyl, and 5-methy 1-6-phenyl derivatives with phosphoryl chloride (483, 829) [N.B. error in work of Minovici and Bente (830)] 2-chloro-5-hydroxypyrazine with phosphoryl chloride (831) 2-chloro-6-hydroxypyrazine with phosphoryl chloride at reflux for 6hours (832) and 2,5-dihydroxy-3-phenylpyrazine and3,5-dihydroxy-2-phenylpyrazine with phosphoryl chloride at 180-200° (829). 

Refluxing phosphoms tribromide converted 2-bromo-3-hydroxy-5,6-diphenyl-pyrazine and 2-bromo-5-hydroxy-3,6-diphenylpyrazine to the dibromopyrazines 2,3-dichloro-5,6-dimethylpyrazine and 2,5-dichloro-3-phenylpyrazine to the dibromopyrazines (817) 5-chloro-2,3-diphenylpyrazine (and its 6-ethyl derivative) to 5-bromo-2,3-diphenylpyrazine (and its 6-ethyl derivative) (866) and 2-hydroxy-... 

Chloropyrazine and derivatives have been shown to react with alkali metal derivatives of a phenylacetonitrile or of a phenylacetamide for example, 2-chloropyrazine treated with diphenylacetonitrile in toluene with sodium amide gave 2-(T-cyano-r,r-diphenylmethyl)pyrazine (68, R = H) (1021, 1022). 2-Chloro-5-phenylpyrazine(s) with diethyl methylmalonate and sodium hydride gave 2-(r,l -di(ethoxycarbonyl)ethyl]-5-phenylpyrazine(s) (363-365, 824, 825), and a similar reaction occurred with 2-chloropyrazine (364, 365,1023). 

Finally, 3-amino-2-cyano-5-phenylpyrazine and ethyl chloroformate gave the N-ethoxy carbonyl derivative 128, which cyclized with loss of ammonia to l-methyl-7-phenylpteridine-2,4-dione in boiling methanolic sodium methoxide (moderate yield).181... 

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