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This table provides a listing of alkyl groups and corresponding structures. Methyl is shown as C H subscript 3 followed by a dash. Ethyl is shown as C H subscript 3 C H subscript 2 followed by a dash. n dash propyl is shown as C H subscript 3 C H subscript 2 C H subscript 2 followed by a dash. Isopropyl is shown as C H subscript 3 C H C H subscript 3 with a dash extending upward from the middle C. n dash butyl is shown as C H subscript 3 C H subscript 2 C H subscript 2 C H subscript 2 followed by a dash. sec dash butyl is shown as C H subscript 3 C H subscript 2 C H C H subscript 3 with a dash extending upward from the third C counting left to right. Isobutyl is shown as C H subscript 3 C H C H subscript 2 with a dash extending to the right. There is a C H subscript 3 bonded to the middle C. tert dash butyl is shown as C H subscript 3 C C H subscript 3 with a C H subscript 3 group bonded below the middle C and a dash extending upward from the central C.
This listing gives the names and formulas for various alkyl groups formed by the removal of hydrogen atoms from different locations.

Note that alkyl groups do not exist as stable independent entities. They are always a part of some larger molecule. The location of an alkyl group on a hydrocarbon chain is indicated in the same way as any other substituent:

This figure shows structures of 3 dash ethylheptane, 2 comma 2 comma 4 dash trimethylpentane, and 4 dash isopropylheptane. The 3 dash ethylheptane structure shows C H subscript 3 C H subscript 2 C H subscript 2 C H subscript 2 C H C H subscript 2 C H subscript 3. Under the C atom labeled 3, is a bond to C H subscript 2 C H subscript 3 which appears in red. The C atoms are labeled 7, 6, 5, 4, 3, 2, and 1 from left to right. The 2 comma 2 comma 4 dash trimethylpentane structure shows C H subscript 3 C bonded to C H subscript 2 C H C H subscript 3. The C atoms are labeled 1, 2, 3, 4, and 5 from left to right. The C atom labeled 2 has a C H subscript 3 bonded above it and below it. The C H subscript 3 groups both appear in red. The C atom labeled 4 has a bond above it to C H subscript 3. The C H subscript 3 group appears in red. The 4 dash isopropylheptane structure shows C H subscript 3 C H subscript 2 C H subscript 2 C H C H subscript 2 C H subscript 2 C H subscript 3. From the fourth C counting from left to right, there is a C H group bonded above. Bonded up and to the right and and up to the left of this C H group are C H subscript 3 groups.

Alkanes are relatively stable molecules, but heat or light will activate reactions that involve the breaking of C–H or C–C single bonds. Combustion is one such reaction:

CH 4 ( g ) + 2 O 2 ( g ) CO 2 ( g ) + 2 H 2 O ( g )

Alkanes burn in the presence of oxygen, a highly exothermic oxidation-reduction reaction that produces carbon dioxide and water. As a consequence, alkanes are excellent fuels. For example, methane, CH 4 , is the principal component of natural gas. Butane, C 4 H 10 , used in camping stoves and lighters is an alkane. Gasoline is a liquid mixture of continuous- and branched-chain alkanes, each containing from five to nine carbon atoms, plus various additives to improve its performance as a fuel. Kerosene, diesel oil, and fuel oil are primarily mixtures of alkanes with higher molecular masses. The main source of these liquid alkane fuels is crude oil, a complex mixture that is separated by fractional distillation. Fractional distillation takes advantage of differences in the boiling points of the components of the mixture (see [link] ). You may recall that boiling point is a function of intermolecular interactions, which was discussed in the chapter on solutions and colloids.

This figure contains a photo of a refinery, showing large columnar structures. A diagram of a fractional distillation column is also shown. Near the bottom of the column, an arrow pointing into the column from the left shows a point of entry for heated crude oil. The column contains several layers at which different components are removed. At the very bottom, residue materials are removed through a pipe as indicated by an arrow out of the column. At each successive level, different materials are removed through pipes proceeding from the bottom to the top of the column. In order from bottom to top, these materials are fuel oil, followed by diesel oil, kerosene, naptha, gasoline, and refinery gas at the very top. To the right of the column diagram, a double sided arrow is shown that is blue at the top and gradually changes color to red moving downward. The blue top of the arrow is labeled, “Small molecules: low boiling point, very volatile, flows easily, ignites easily.” The red bottom of the arrow is labeled, “Large molecules: high boiling point, not very volatile, does not flow easily, does not ignite easily.”
In a column for the fractional distillation of crude oil, oil heated to about 425 °C in the furnace vaporizes when it enters the base of the tower. The vapors rise through bubble caps in a series of trays in the tower. As the vapors gradually cool, fractions of higher, then of lower, boiling points condense to liquids and are drawn off. (credit left: modification of work by Luigi Chiesa)

In a substitution reaction    , another typical reaction of alkanes, one or more of the alkane’s hydrogen atoms is replaced with a different atom or group of atoms. No carbon-carbon bonds are broken in these reactions, and the hybridization of the carbon atoms does not change. For example, the reaction between ethane and molecular chlorine depicted here is a substitution reaction:

This diagram illustrates the reaction of ethane and C l subscript 2 to form chloroethane. In this reaction, the structural formula of ethane is shown with two C atoms bonded together and three H atoms bonded to each C atom. The H atom on the far right is red. Ethane is added to C l bonded to C l, followed by an arrow that points right. The arrow is labeled, “Heat or light.” To the right, the chloroethane molecule is shown with two C atoms bonded together. The left C atom has three H atoms bonded to it, but the right C atom has two H atoms bonded above and below it along with a C l atom. The C l atom appears in red with 3 pairs of electron dots at the right end of the molecule. This is followed by a plus sign, which in turn is followed in red by H bonded to C l. Three pairs of electron dots are present above, to the right, and below the C l.

The C–Cl portion of the chloroethane molecule is an example of a functional group    , the part or moiety of a molecule that imparts a specific chemical reactivity. The types of functional groups present in an organic molecule are major determinants of its chemical properties and are used as a means of classifying organic compounds as detailed in the remaining sections of this chapter.


Organic compounds that contain one or more double or triple bonds between carbon atoms are described as unsaturated. You have likely heard of unsaturated fats. These are complex organic molecules with long chains of carbon atoms, which contain at least one double bond between carbon atoms. Unsaturated hydrocarbon molecules that contain one or more double bonds are called alkenes . Carbon atoms linked by a double bond are bound together by two bonds, one σ bond and one π bond. Double and triple bonds give rise to a different geometry around the carbon atom that participates in them, leading to important differences in molecular shape and properties. The differing geometries are responsible for the different properties of unsaturated versus saturated fats.

Questions & Answers

what is an atom
Precious Reply
An atom is the smallest particle of an element which can take part in a chemical reaction..
how to find the rate of reaction?
what is isomerism ?
Lucky Reply
Formula for equilibrium
Danmori Reply
is it equilibrium constant
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Imhologhomhe Reply
chemical formula for water
Muhammad Reply
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Maryam Reply
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How can water be turned to gas
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Okiemute Reply
how does carbon catenate?
obuke Reply
condition in cracking from Diesel to petrol
Brient Reply
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i also
I also
condition for cracking diesel to form kerosene
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what is periodic law
rotimi Reply
periodic law state that the physical and chemical properties of an element is the periodic function of their atomic number
how is valency calculated
Ashley Reply
How is velency calculated
Hi am Isaac, The number of electrons within the outer shell of the element determine its valency . To calculate the valency of an element(or molecule, for that matter), there are multiple methods. ... The valency of an atom is equal to the number of electrons in the outer shell if that number is fou
what is the oxidation number of this compound fecl2,fecl3,fe2o3
Asmau Reply
bonds formed in an endothermic reaction are weaker than the reactants but y r these compound stable at higher temperatures
zille Reply
what is a disproportionation reaction
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