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 C_n-1H_2n-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.