Answer to Question #77691 in Organic Chemistry for Esma Sherwani

Question

Arrange the following sets of compounds in order of increasing acid strength. Briefly explain your answer.
i) Acetic acid, monochloracetic acid, dichloracetic acid, trichloracetic acid
ii) Acetic acid, succinic acid, malonic acid (compare first dissociation only)

Answer 1

Answer:
i) Chlorine is acceptor of electrons and it stabilizes the carboxylate anion. The more
chlorine atoms in alpha-position of acetic acid - the more acidity. Therefore:
Acetic acid
Monochloracetic acid
Dichloracetic acid
Trichloracetic acid
ii) The similar situation. Malonic acid can be described as -COOH substituted acetic acid.
-COOH group is strong acceptor of electons. Succinic acid can be described as -CH2COOH
substituted acetic acid. -CH2COOH is weak acceptor of electrons. Therefore:
Acetic acid
Succinic acid
Malonic acid