Model solutions of the dipeptide glycylphenylalanine were chlorinated at pH 7.0 to five different chlorine-to-peptide (Cl 2 /peptide) mole ratios and analyzed after 30 min by highperformance liquid chromatography. At Cl 2 /peptide mole ratios e 1, N-chloroglycylphenylalanine (I) appears to be the only product. At mole ratios g 2, N,N-dichloroglycylphenylalanine (II) was the only product. II decomposes in model solutions (t 1/2 ) 6.4 h) at pH 7.0 to form a compound tentatively identified as N-[2-(N′-chloroimino)ethanoyl]phenylalanine (III), an N-chloroaldimine. III, in turn, decomposes (t 1/2 ) 36 h) to IV. From 13 C-and 1 H-NMR, GC/MS, and IR, IV was identified as N-cyanoacylphenylalanine. Glycylp-[ 3 H]-phenylalanine (VI) was synthesized in order to monitor the reaction at low concentrations of the compound in a wastewater. A secondary wastewater (TKN ) 1.29 mg of N/L; [NH 3 ]) 0.074 mg of N/L) was inoculated with VI and chlorinated to nine different chlorine concentrations. The stabilities of the tritiated analogs of II and III in the wastewater were comparable to those determined in model solutions. ES960794A X Abstract published in Advance ACS Abstracts, May 1, 1997.FIGURE 6. Breakpoint curve of a secondary wastewater and the corresponding glycyl-p-[ 3 H]-phenylalanine chlorination products determined 30 min after chlorinating to nine different concentrations of aqueous chlorine (1-9 mg of Cl2/L).
Products of the 30-min chlorination of the dipeptide alanylphenylalanine were determined at pH 7.0 in model
solutions.
At Cl2/peptide mole ratios ≤1,
N-chloroalanylphenylalanine
(I) is the only product. I is very stable at
23 °C (t
1/2 = 111
± 8.8 h). At mole ratios ≥2,
N,N-dichloroalanylphenylalanine
(II) is the only product. II decomposes in
model solutions
(t
1/
2 = 4.1 ± 0.2 h) at pH 7.0
to form a compound identified
as the N-chloroketimine
N-[2-(N ‘-chloroimino)propanoyl]phenylalanine (III). The structure of III was
identified by
converting it to N-pyruvylphenylalanine
tert-butyl ester
by reduction, hydrolysis, and esterification and
correlating
the mass spectrum and GC retention time of this derivative
with those of an authentic sample. III is unusually
stable and
decomposes slowly (t
1/2 = 125 ± 6.5 h) to
phenylalanine.
In order to monitor the reactions of the dipeptide at
low
concentrations in a wastewater,
alanyl-p-[3H]-phenylalanine
was synthesized. A primary wastewater (TKN = 19.82
mg/L; [NH3] = 19.79 mg/L) was inoculated with
the
radiolabeled dipeptide and chlorinated to seven different
chlorine concentrations spanning the breakpoint curve
of the wastewater. Products identical to those
observed
in model solutions were formed. The stabilities of
the
tritiated analogs of II and III in the wastewater
were similar
to those determined in model solutions. Time studies
of
the decomposition of
N,N-dichloroalanyl-p-[3H]-phenylalanine
revealed the formation of an intermediate (A) not
previously
recognized. Modeling of the reactions of II suggested
that
A was a decomposition product of III in the
formation
of phenylalanine and was probably either an isocyanate or
a carbamic acid formed from hydrolysis of an isocyanate
intermediate.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.