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Homologous series
 
 
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In chemistry
Chemistry

Chemistry is the science concerned with the composition, structure, and properties of matter, as well as the changes it undergoes during chemical reactions....
, a homologous series is a series of organic compound
Organic compound

An organic compound is any member of a large class of chemical compounds whose molecules contain carbon. For historical reasons discussed below, a few types of compounds such as carbonates, simple oxides of carbon and cyanides, as well as the allotropes of carbon, are considered Inorganic compound....
s with a similar general formula, possessing similar chemical properties due to the presence of the same functional group
Functional group

In organic chemistry, functional groups are specific groups of atoms within molecules that are responsible for the characteristic chemical reactions of those molecules....
, and shows a gradation in physical properties as a result of increase in molecular size and mass (see relative molecular mass). For example, ethane has a higher boiling point than methane since it has more Van der Waals forces(intermolecular forces) with neighbouring molecules.






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In chemistry
Chemistry

Chemistry is the science concerned with the composition, structure, and properties of matter, as well as the changes it undergoes during chemical reactions....
, a homologous series is a series of organic compound
Organic compound

An organic compound is any member of a large class of chemical compounds whose molecules contain carbon. For historical reasons discussed below, a few types of compounds such as carbonates, simple oxides of carbon and cyanides, as well as the allotropes of carbon, are considered Inorganic compound....
s with a similar general formula, possessing similar chemical properties due to the presence of the same functional group
Functional group

In organic chemistry, functional groups are specific groups of atoms within molecules that are responsible for the characteristic chemical reactions of those molecules....
, and shows a gradation in physical properties as a result of increase in molecular size and mass (see relative molecular mass). For example, ethane has a higher boiling point than methane since it has more Van der Waals forces(intermolecular forces) with neighbouring molecules. This is due to the increase in the number of atoms making up the molecule. Organic compounds in the same homologous series vary by a CH2.

Alkane
Alkane

Alkanes, also known as paraffins, are chemical compounds that consist only of the elements carbon and hydrogen , wherein these atoms are linked together exclusively by single bonds without any cyclic structure ....
s (paraffin
Paraffin

In chemistry, paraffin is the common name for the alkane hydrocarbons with the general formula CnH2n+2. Paraffin wax refers to the solids with n=20–40....
s), alkene
Alkene

In organic chemistry, an alkene, olefin, or olefine is an Saturation chemical compound containing at least one carbon-to-carbon double bond....
s (olefins), methoxyethane
Methoxyethane

Methoxyethane, also known as methyl ethyl ether, is a colorless gaseous ether with a medicine-like odor. It is extremely flammable, and its inhalation may cause asphyxiation or dizzyness....
 (ethers), and alkyne
Alkyne

Alkynes are hydrocarbons that have at least one triple bond between two carbon atoms, with the formula CnH2n-2. The alkynes are traditionally known as acetylenes or the acetylene series, although the name acetylene is also used to refer specifically to the simplest member of the series, known as e...
s (acetylene
Acetylene

Acetylene is the chemical compound with the symbol carbonhydrogen. It is the simplest alkyne.As an alkyne, acetylene is Saturation because its two carbon atoms are Chemical bond together in a triple bond....
s) form such series in which members differ in mass by 14 atomic mass units. For example, the alkane homologous series begins with methane
Methane

Methane is a chemical compound with the molecular formula . It is the simplest alkane, and the principal component of natural gas. Methane's bond angles are 109.5 degrees....
 (CH4), ethane
Ethane

Ethane is a chemical compound with chemical formula C2H6. It is the only two-carbon alkane, that is, an aliphatic hydrocarbon....
 (C2H6), propane
Propane

Propane is a three-carbon alkane, normally a gas, but compressible to a transportable liquid. It is derived from other petroleum products during oil or natural gas processing....
 (C3H8), butane
Butane

Butane, also called n-butane, is the unbranched alkane with four carbon atoms, CH3CH2CH2CH3....
 (C4H10), and pentane
Pentane

Pentane is any or one of the organic compounds with the chemical formula C5H12. This alkane is a component of some fuels and is employed as a specialty solvent in the laboratory....
 (C5H12), each member differing from the previous one by a CH2 group (or 14 atomic mass
Atomic mass

The atomic mass is the mass of an atom, most often expressed in Atomic mass units. The atomic mass may be considered to be the total mass of protons, neutrons and electrons in a single atom ....
 units).

Similarly, there is the alcohol
Alcohol

In chemistry, an alcohol is any organic compound in which a hydroxyl Functional group is bound to a carbon atom of an alkyl or substituted alkyl group....
 homologous series that starts with methanol
Methanol

Methanol, also known as methyl alcohol, carbinol, wood alcohol, wood naphtha or wood spirits, is a chemical compound with chemical formula carbonhydrogen3oxygenhydrogen ....
 (CH4O), ethanol
Ethanol

Ethanol, also called ethyl alcohol, pure alcohol, grain alcohol, or drinking alcohol, is a volatility , flammable, colorless liquid....
 (C2H6O), as primary alcohols, isopropanol (C3H8O) as a simple secondary alcohol, and a simple tertiary alcohol is tert-butanol
Butanol

Butanol or butyl alcohol , is a primary alcohol with a 4 carbon structure and the molecular formula of Carbon4Hydrogen9Oxygen....
 (C4H10O).

Even while the general formulae are the same, they have different structures that can lead the exact same compound to different properties, although they will always present the same chemical properties while as a homologous compound.

Compounds in each set have the same little group of atoms called the functional group
Functional group

In organic chemistry, functional groups are specific groups of atoms within molecules that are responsible for the characteristic chemical reactions of those molecules....
. Most chemical properties of organic compounds are due to the presence of the functional group
Functional group

In organic chemistry, functional groups are specific groups of atoms within molecules that are responsible for the characteristic chemical reactions of those molecules....
.














































Homologous seriesGeneral formulaExampleFunctional group
Straight Chain AlkanesCnH2n + 2 (n = 1)CH4, n = 1
Alkyl
Alkyl

An alkyl is a univalent Radical consisting of carbon and hydrogen atoms, arranged in a chain. The Alkyls form homologous series with the general formula CnH2n+1....
CnH2n + 1 (n = 1)CH3, n = 1
Alkenes and Cyclic AlkanesCnH2n (n = 2)C2H4, n = 2C = C
AlkynesCnH2n − 2 (n = 2)C2H2, n = 2C = C
AlcoholsCnH2n + 1OH (n = 1)CH4O, n = 1- OH
Carboxylic acid
Carboxylic acid

Carboxylic acids are organic acids characterized by the presence of a carboxyl group, which has the Chemical formula -COH, usually written -COOH or -CO2H....
s		CnH2nO2 (n = 1)CH2O2, n = 1- COOH
Carbohydrate
Carbohydrate

Carbohydrates or saccharides are the most abundant of the four major classes of biomolecules. They fill numerous roles in living things, such as the storage and transport of energy and structural components ....
s		Cn(H2O)n (n = 1)C6H12O6
Where n represents the number of carbon atoms present.

A Homologation reaction
Homologation reaction

A homologation reaction, also known as homologization, is any chemical reaction that effects an overall increase of the carbon skeleton of a saturated reactant molecule....
 is any chemical process
Chemical process

In a "Process " sense, a chemical process is a method or means of somehow changing one or more chemicals or chemical compounds. Such a chemical process can occur by itself or be caused by somebody....
 converting one member of a homologous series to the next.

Homologous Oxides


Homologous series are not unique to organic chemistry. Titanium
Titanium

Titanium is a chemical element with the symbol Ti and atomic number 22. Sometimes called the ?space age metal?, it has a low density and is a strong, lustrous, corrosion-resistant transition metal with a silver colour....
, vanadium
Vanadium

Vanadium is the chemical element with the symbol V and atomic number 23. It is a soft, silvery grey, ductile transition metal. The formation of an oxide layer stabilizes the metal against oxidation....
, and molybdenum
Molybdenum

Molybdenum , is a Group 6 element chemical element with the symbol Mo and atomic number 42. It has the List of elements by melting point melting point of any element....
 oxides all form homologous series. E.g. VnO2n-1 for 2 < n < 10