2-Chloropropionic acid

2-Chloropropionic acid is the chemical compound with the formula CH₃CHClCO₂H. This colorless liquid is the simplest chiral chlorocarboxylic acid, and it is noteworthy for being readily available as a single enantiomer.

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Preparation and use in organic synthesis

Enantiomerically pure S-2-chloropropionic acid is prepared from alanine via diazotization in hydrochloric acid.^[1] Other α-amino acids undergo this reaction.

Reduction of S-2-chloropropionic acid with lithium aluminium hydride affords S-2-chloropropanol, the simplest chloro-alcohol. This alcohol undergoes cyclization upon treatment potassium hydroxide, which causes dehydrohalogenation to give the epoxide, R-methyloxirane.^[2]

Safety

In general, α-halocarboxylic acids and their esters are good alkylating agents and should be handled with care. 2-Chloropropionic acid is a neurotoxin.^[3]

References

1. ^ Koppenhoefer, B.; Schurig, V. “S-2-Chloroalkanoic Acids of High Enantiomeric Purity from (S)-2-Amino Acids: (S)-2-Chloropropanoic Acid” Organic Syntheses, Collected Volume 8, p.119 (1993). [1]
2. ^ Koppenhoefer, B.; Schurig, V. (R)-Alkyloxiranes of Hight Enantiomeric Purity from (S)-2-Chloroalkanoic Acids via (S)-2-Chloro-1-Alkanols: (R)-Methyloxirane” Organic Syntheses, Coll. Vol. 8, p.434 (1993). [2]
3. ^ Simpson MG, Wyatt I, Jones HB, Gyte AJ, Widdowson PS, Lock EA. (1996). "Neuropathological changes in rat brain following oral administration of 2-chloropropionic acid.". Neurotoxicology 17 (2): 471-80. PMID 8856742.