Question

How do functional groups affect organic molecules?

Answer 1

Functional groups determine the identity of organic molecules

Explanation:

Functional groups are very important in organic chemistry since they determine the identity of these molecules and therefore, depict the chemical and physical properties of them.

For example, hydroxy groups `OH` is specific for alcohols. the general structure for alcohols is `R-OH`.

In a similar way, `COOH` is the functional group for carboxylic acids of a general structure `R-COOH`.

For esters, the functional group is `COOR'`, where esters have the general structure `R-COOR'`.

And so on.

with different functional groups, alcohols, carboxylic acids, and esters have different chemical and physical properties and therefore, different identity.

Let us take a specific example; Propane `CH_3CH_2CH_3`. Propane is a gaseous molecule at room temperature. Adding a hydroxy group to its structure we get `CH_3CH_2CH_2-OH` which is the propanol. Propanol is liquid at room temperature ( change on physical property ). Propanol can react thanks to the presence of the oxygen atom in its backbone, however, propane has very limited reactivity ( change on chemical property ).

There are many other functional groups such as:
Sulfides: `R-S-R'`
Thiols: `R-SH`
Ethers: `R-O-R'`
Anhydrides: `R-CO-O-CO-R'`
Ketones: `R-CO-R'`
Aldehydes: `R-CO-H`
Amides: `R-CO-N(R')_2` or `R-CO-NH_2` or `R-CO-NHR'`
Amines: `R-NH_2` or `R-NHR'` or `R-N(R')_2`
Nitriles: `R-CN`
Alkyl halides: `R-X` where `X` is an element from group 17.
Alkenes: `R-CH=CH-R'`
Alkynes: `R-C-=C-R'`
etc.