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प्रश्न
What is a homologous series?
What is a homologous series? Explain with an example.
उत्तर १
Homologous series is a group of organic compounds with a similar structure and similar chemical properties in which the successive compounds differ by a CH2 group.
उत्तर २
A homologous series is a series of carbon compounds that have different numbers of carbon atoms but contain the same functional group.
For example, methane, ethane, propane, butane, etc. are all part of the alkane homologous series. The general formula of this series is CnH2n+2.
Methane CH4
Ethane CH3CH3
Propane CH3CH2CH3
Butane CH3CH2CH2CH3
It can be noticed that there is a difference of -CH2 unit between each successive compound.
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संबंधित प्रश्न
What is meant by homologous series of carbon compounds?
Classify the following carbon compounds into two homologous series and name them.
C3H4, C3H6, C4H6, C4H8, C5H8, C5H10
Write the name and formula of the 2nd member of homologous series having general formula CnH2n + 2.
The following vegetables are kept in a basket :
Potato, Tomato, Radish, Brinjal, Carrot, Bottle-gourd
Which two of these vegetables correctly represent the homologous structures?
(A) Carrot and Tomato
(B) Potato and Brinjal
(C) Radish and Carrot
(D) Radish and Bottle-gourd
Write the names and formulae for the first three members of the homologous series for chloroalkanes.
What is a homologous series? Explain with an example.
The molecular formula of an organic compound is C18H36. Name its homologous series.
The molecular formula of a homologue of butane is:
(a) C4H8
(b) C3H6
(c) C4H6
(d) C3H8
The number of carbon atoms present in the molecule of fifth member of the homologous series of alkynes is:
(a) four
(b) five
(c) six
(d) seven
The molecular formula of the third member of the homologous series of ketones is:
(a) C4H8O
(b) C3H6O
(c) C5H10O
(d) C6H12O
Give the dot diagram of the first member of the alcohol.
Give the abbreviated formula of the third member of the alcohol.
Write the name and molecular formula of the first member of the homologous series of alkynes.
Study the different conclusions drawn by students of a class on the basis of observations of preserved/available specimens of plants and animals.
I. Potato and sweet potato are analogous organs in plants.
II. Wings of insects and wings of birds are homologous organs in animals.
III. Wings of insects and wings of bats are analogous organs in animals.
IV. Thorns of citrus and tendrils of cucurbita are analogous organs in plants.
The correct conclusions are:
(A) I, and II
(B) II and IV
(C) I and III
(D) III and IV
Copy and complete the following table which relates to three homologus series of hydrocarbons:
| General formula | CnH2n | CnH2n-2 | CnH2n+2 |
| IUPAC name of the homologus series | |||
| Characteristic bond type | Single bonds | ||
| IUPAC name of the first member of the series | |||
| Type of reaction with chlorine | Addition |
Write the name and formula of the fourth member of the following homologous series:
Alkyne
What is a homologous series?
The unsaturated hydrocarbons containing a carbon-carbon double bond are called _______.
Find the odd one out and give its explanation.
As one ascends in any homologous series, physical properties change gradually.
Complete the following table for the homologous series of alkanes.
| Name | Molecular formula | Condensed structural formula | Number of carbon atom | Number of -CH2- units | Boiling point °C |
| Methane | CH4 | CH4 | 1 | 1 | -162 |
| Ethane | C2H6 | CH3–CH3 | 2 | 2 | -88.5 |
| Propane | C3H8 | CH3–CH2–CH3 | 3 | 3 | -42 |
| Butane | C4H10 | CH3–CH2–CH2–CH3 | ______ | ______ | 0 |
| Pentane | C5H12 | CH3–CH2–CH2–CH2–CH3 | ______ | ______ | 36 |
| Hexane | C6H14 | CH3–CH2–CH2–CH2–CH2–CH3 | ______ | ______ | 69 |
Complete the following table for homologous series of alcohols.
| Name | Molecular formula | Condensed structural formula | Number of carbon atom | Number of -CH2- units | Boiling point °C |
| Methanol | CH4O | CH3-OH | 1 | 1 | 63 |
| Ethanol | C2H6O | CH3–CH2-OH | 2 | 2 | 78 |
| Propanol | C3H8O | CH3–CH2–CH2-OH | ______ | ______ | 97 |
| Butanol | C4H10O | CH3–CH2–CH2–CH2–OH | ______ | ______ | 118 |
Complete the following chart by using examples given in brackets.
(isobutylene, cyclohexane, propane, cyclohexene, cyclopentane, benzene, propyne, isobutane, propene)
| Straight chain hydrocarbons | Branched chain hydrocarbons | Cyclic hydrocarbons |
Which of the following pairs can be the successive members of a homologous series?
What is called homologous series? Give any three of its characteristics?
Successive members of a homologous series vary by how many atomic mass unit?
The first member of alkyne homologous series is
A carbon compound ‘A’ having melting point 156K and boiling point 351K, with molecular formula C2H6O is soluble in water in all proportions.
- Identify ‘A’ and draw its electron dot structure.
- Give the molecular formulae of any two homologues of ‘A’.
Consider the carbon compounds having following molecular formula:
(i) C2H2 (ii) C2H5 (iii) C3H7OH (iv) C2H6COOH (v) CH3CHO
- Identify which one of the above compounds, is a member of aldehyde series.
- Write the general formula of the series to which compound C2H2 belongs.
- Which one of the above compounds has triple bonds between carbon-carbon atoms?
- Write the molecular formula of the first member of the homologous series to which the compound C3H7OH belongs.
Name the following:
Group of organic compounds where the successive members follow a regular structural pattern, successive compounds differ by a 'CH2' group.
