Tuesday 15 December 2015

Lecture 3 – Homologous series of Carboxylic Acids

ACKNOWLEDGEMENT:

Figure
Source of Figure
Figure 17b
http://www.ck12.org
Figure Table 7a
http://www.restauro-online.com/
Figure Table 7b
http://howtosmile.org/
Figure Table 7c
http://www.wikiwand.com/
Figure Table 7d
http://www.wikiwand.com/








Carboxylic Acids:

Carboxylic acids are naturally occurring acids. They are weakly ionized in nature. They form a homologous series of organic compounds with the carboxylic functional group or –COOH. Each successive member of the series differ by CH2, and the general formula of the series is Cn-1H2n-1COOH. The functional group, –COOH gives the compound its acidic properties and in aqueous solutions, the H radical in –COOH is ionnized to give H+ ions. The H+ ions are responsible for the acid behaviour of the compound.  

Figure 17b shows the functional group.

Figure 17b:


Table 7: First 4 carboxylic acids in the carboxyl homologous series

Carboxylic Acid
Common name
Formula
Physical Structure

Methanoic Acid

Formic Acid

H3COOH


Ethanoic Acid

Acetic Acid
(Vinegar)

CH3COOH
 

Propanoic Acid

-

C2H5COOH

Butanoic Acid

-

C3H7COOH


Chemical properties of carboxylic acids:

Carboxylic acids are weak acids, implying that they are only partially ionized in their aqueous solutions. They, however react with metals, bases and carbonates like any other acid.
  • Carboxylic acids turn moist blue litmus paper to red.
  • Reaction with metals:
    • Acids react with metals to form salt and Hydrogen gas.
  • Reaction with metal oxides:
    • Acids react with metal oxides to form salt and water.
  •  Reaction with metal hydroxides:
    • Acids react with metal hydroxides to form salt and water. This is called the neutralization reaction.
  • Reaction with metal carbonates:Acids react with metal carbonates to form salt, water and Carbon dioxide gas.