Carboxylic acids having atleast one `alpha`-hydrogen react with `Cl_(2) or Br_(2)` in the presence of phosphorus ( or a phosphorus halide) to give `alpha`-halo acids. This reaction is known as Hell-Volhard-Zelinsky reaction (HVZ reaction),
`R-CH_(2)COOHunderset(Delta)overset(P//Br_(2))toR-overset(Br)overset(|)"CH"-COOH`
The HVZ reaction is limited to the formation of `alpha`-chloro and a-bromo acids and it is sometimes awkward to carry out. The reagents ( `X_(2)` and P) are noxious and the reaction time is often long and the conditions of reaction are harsh.
`CH_(3)CH_(2)COOHoverset(Red P +Br_(2))to(A)overset(alc. KOH)(B)`. The product (B) is :
A. 2-ketopropanoic acid
B. acrylic acid
C. 2-hydroxypropanoic acid
D. 2-aminopropanoic acid
