Page 281 - Chemistry ICSE Class X

Organic Chemistry 267

(Here, in both the formulae, the chain length remains the same)
ƒ Pentyne has the following position isomers:

ƒ Propanol (C H OH) has the following position isomers:
7
3

/Ŷ ĐĞƌƚĂŝŶ ĐŽŵƉŽƵŶĚƐ ŽĨ ĐĂƌďŽŶ͕ ŽŶĞ
Žƌ ŵŽƌĞ ŽĨ ŚLJĚƌŽŐĞŶƐ ďŽŶĚĞĚ ƚŽ
Functional Groups ĐĂƌďŽŶ ĂƌĞ ƌĞƉůĂĐĞĚ ďLJ ƚŚĞ ĂƚŽŵƐ ŽĨ
ƐŽŵĞ ŽƚŚĞƌ ĞůĞŵĞŶƚ;ƐͿ͘ ^ƵĐŚ ĂƚŽŵƐ
are called heteroatoms͘ dŚĞƐĞ
What is a functional group ŚĞƚĞƌŽĂƚŽŵƐ ŝŵƉĂƌƚ ĐĞƌƚĂŝŶ ƐƉĞĐŝĮĐ
# HWPEVKQPCN ITQWR KU FGſPGF CU HQNNQYU ƉƌŽƉĞƌƟĞƐ ƚŽ ƚŚĞ ĐŽŵƉŽƵŶĚ͘
An atom or a group of atoms which gives some characteristic
properties to a compound is called a functional group.
# HWPEVKQPCN ITQWR ECP CNUQ DG FGſPGF CU HQNNQYU
An atom or a group of atoms which is usually the site of chemical
reactivity in an organic molecule is called its functional group.
Some common functional groups are given in Table 12.1.

Table 12.1 Some common functional groups
Formula of Name of functional Formula of the Name of the compound containing
functional group group compound containing the functional group
the functional group
– OH Hydroxyl (or Alcoholic) C H OH Ethanol (or Ethyl alcohol)
5
2
– CHO Aldehydic HCHO Methanal (or Formaldehyde)
.
.
– Ketonic CH CO CH Propanone (or Acetone)
CO 3 3
–
– COOH Carboxyl (or Carboxylic) CH COOH Ethanoic acid (or Acetic acid)
3
– X (halogen) Halo CH Cl Chloromethane (or Methyl chloride)
3
– NH 2 Amino CH NH 2 Methanamine (or Methylamine)
3
– NO 2 Nitro CH NO 2 Nitromethane
3
– – Double bond CH = CH 2 Ethene (or Ethylene)
2
–
C = C –
– C { C – Triple bond HC { CH Ethyne (or Acetylene)
What are the characteristics of a functional group
Some characteristics of a functional group are listed below:
ƒ The functional group acts as the reactive site in a molecule. dŚĞ ĨƵŶĐƟŽŶĂů ŐƌŽƵƉ ŝƐ ĂƩĂĐŚĞĚ ƚŽ
ƒ All compounds having the same functional group belong to the same ƚŚĞ ĐĂƌďŽŶ ĐŚĂŝŶ ƚŚƌŽƵŐŚ ŝƚƐ ĨƌĞĞ
family. Such a family is called homologous series. For example, all ǀĂůĞŶĐLJ Žƌ ǀĂůĞŶĐŝĞƐ͘
compounds containing – OH group belong to the alcohol series.
ƒ The chemical properties of the compounds containing the same
functional group are similar. For example, all compounds containing
– OH group attached to an alkyl group are called alcohols. All alcohols
show similar properties.