|Table of contents|
|Chains, Branches and Rings|
|Will you be my friend? (functional group)|
|Nomenclature of Carbon Compounds|
The hydrocarbons may have branched, closed chains or ring or cyclic structures.
The alkanes containing three or less carbon atoms do not form branches.
- A branched structure occurs when the carbon atoms are not arranged in a straight chain but instead have additional carbon branches attached to them.
- In the given options, CH4 (methane) does not have any branches and forms a straight chain.
- CH3-CH3 (ethane) also does not have any branches and forms a straight chain.
- CH3-CH2-CH3 (propane) has a branched structure as it contains a central carbon atom with two additional carbon branches attached to it.
- C4H10 (butane) has two possible arrangements of carbon atoms. One is a straight chain with no branches, and the other has a branched structure with one carbon branch attached to the central carbon atom.
- Therefore, the correct answer is Option C: CH3-CH2-CH3, which has a branched structure.
These hydrocarbons contain closed chain or rings of atoms in their molecules. These are of two types:
(A) Alicyclic hydrocarbon:
(B) Aromatic hydrocarbon:
Properties of CH3-OH and CH3-CH2OH are similar and it is due to the presence of -OH (hydroxyl) group.
This group is known as alcoholic group.
Family of compounds having -OH group is called alcohols.
"A series of organic compounds having similar structures similar chemical properties and same general formula in which the successive members differ in their molecular formula by -CH2 group".
The different members of the series are called homologous.
- These cyclic compounds are named by prefixing "cyclo" before the name of the corresponding straight-chain hydrocarbon.
- Aromatic hydrocarbons have at least one benzene ring in their molecules, while alcoholic hydrocarbons have the -OH (hydroxyl) group.
- Alkyl hydrocarbons are not specifically related to rings or functional groups.
Therefore, the correct answer is Option A: Alicyclic hydrocarbon.
Q. What is a homologous series? Explain with an example.
(i) Yes, all these compounds are the members of a homologous series for alcohols.
(ii) CH3OH, C2H5OH, C3H7OH and C4H9OH -increasing carbon atoms. These four compounds form a homologous series.
HCHO, CH3CHO, CH3CH2CHO, CH3CH2CH2CHO
Carboxylic acids: HCOOH, CH3COOH, CH3CH2COOH, CH3CH2CH2COOH
Amines: CH3NH2, CH3CH2NH2,CH3 CH2CH2NH2.
Ketones: CH3COCH3, CH3COCH2CH3, CH3COCH2CH2CH 3
Haloalkanes: CH3X, CH3CH2X, CH3CH2CH2X, CH3CH2CH2-CH2X
Q. How do physical properties change in a homologous series of hydrocarbons?
The physical properties of the various members of a homologous series change regularly with an increase in the molecular mass.
(i) Melting and Boiling Points : Melting point and boiling point of hydrocarbon in a homologous series increases with an increase in molecular mass.
(ii) Physical State:
Hydrocarbons containing lesser number of carbon atoms are gases.
Hydrocarbons containing large number of carbon atoms are solids.
Hydrocarbon containing intermediate number of carbon atoms are liquids.
Example: Hydrocarbon containing 1-4 carbon atoms are gases, these containing 5-16 carbon atoms are liquid and those containing more than 16 carbon atoms are solids.
Carbon compounds can be called by their common names, but, then remembering millions of compounds by their individual names may be very difficult. Due to this reason, the International Union of Pure and Applied chemistry (IUPAC) has devised a very systematic method of naming these compounds.
|No. of carbon atom||Stem|
Example: Saturated hydrocarbon.
Alkane → Meth + ane = Methane
Alkene → Eth + ene = Ethene
Alkyne → Eth + yne = Ethyne
"Functional group may be defined as an atom or a group of atoms which is responsible for most of the characteristic chemical properties of an organic compound".
Prefixes and Suffixes of some Substituents/Functional Group
|1. What are functional groups in carbon compounds?|
|2. What is the difference between a chain, branch, and ring in carbon compounds?|
|3. What is a homologous series in carbon compounds?|
|4. What is the nomenclature of carbon compounds?|
|5. How do chains, branches, and rings affect the physical and chemical properties of carbon compounds?|