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Alkanes - Definition. Properties, Formulas, FAQs

Alkanes - Definition. Properties, Formulas, FAQs

Edited By Team Careers360 | Updated on Jul 02, 2025 04:24 PM IST

A series of compounds containing Hydrogen and carbon atoms with a single covalent bond constitutes an alkane series. There are compounds in this category comprised of carbon and hydrogen atoms linked by one covalent bond. It also appears to contain a Homologous Series of compounds with a molecular general formula of alkane of CnH2n+2.

This Story also Contains
  1. Hydrocarbons
  2. Alkanes: Physical Properties
  3. Formula and Alkane Structure of Alkanes
  4. Chemistry of Alkane Formulas
  5. Alkane Formula with Branched Chains
  6. Groups and Alkyls
Alkanes - Definition. Properties, Formulas, FAQs
Alkanes - Definition. Properties, Formulas, FAQs

All alkanes can be divided into two groups based on their structure. Carbon and hydrogen are the only elements in them. One bond form between each hydrogen atom and four bonds between each carbon atom.

Hydrocarbons

Its molecular formula is CH4 and it comes from the simple alkane methane ethane propane-butane. Alkane structural formula is for a compound with only one covalent bond

Methane

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Methane

An additional carbon atom is attached to another carbon atom via a covalent bond in a long-chain alkane molecule. A total of four single covalent bonds are formed between each atom and enough hydrogen atoms. Oxana is a long-chained hydrocarbon. Alkanes with eight carbons have the molecular formula C8H18.

Alkanes: Physical Properties

1.Alkane Solubility

  1. Generally speaking, alkanes are non-polar molecules due to the fact that carbon and hydrogen have little difference in Electronegativity, and they have a covalent bond between them.

  2. A general rule of thumb is that polar molecules are soluble in polar solvents, whereas nonpolar molecules are soluble in nonpolar ones. The nature of alkanes, therefore, is hydrophobic, meaning they are insoluble in water.

  3. They are however soluble in organic solvents since overcoming existing Van Der Waals Forces and generating new ones takes about the same amount of energy.

2. Alkanes and their boiling points

  1. With increasing molecular weight, alkanes have a higher boiling point,

  2. A comparison of the boiling points of straight-chain alkanes and their structural isomers reveals the former has a higher boiling point.

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3.The melting points of alkanes

  1. An alkane's melting point increases as its molecular weight increases, i.e., it is proportional to its boiling point.

  2. There is a strong attraction between alkanes that makes it hard to overcome them due to their solid nature.

  3. The melting point of even-numbered alkanes tends to be higher than that of odd-numbered alkanes because the even-numbered alkanes form well-organized crystal alkane structures in solid-state, making them difficult to seep out.


Formula and Alkane Structure of Alkanes

Condensed forms of alkane structural formulas are available. Pentane is a chemical compound containing three CH2 methylene groups in the middle of the chain.The structural formula can be written by grouping them together. The first five unbranched alkane formulas are listed below.

Name

The molecular formula of alkane

The condensed structural formula of alkane

methane

CH4

CH4

ethane

C2H6

CH3CH3

propane

C3H8

CH3CH2CH3

butane

C4H10

CH3(CH2)2CH3







Chemistry of Alkane Formulas

There is a wide variety of information to be found in organic compound formulas. The atomic numbers for molecules of a compound can be calculated by looking at a molecular formula, like the one for octane. Alkanes have various properties, including chemical, physical, and physicochemical, and the Molecular Formula of C8H18 can apply to many of them.

Each of these compounds has a specific alkane structure formula showing the atoms in the molecule arranged in a certain order. Isomerization refers to the process of changing the alkane structure of organic compounds with the same molecular formula.

There are many organic compounds that can be converted into alkanes. The functional groups of many organic molecules are alkane groups substituted for the hydrogen atom of the basic molecule. Because of these factors, alkanes are sometimes named for organic compounds.

Alkane Formula with Branched Chains

Alkanes contain carbon atoms that form straight chains, branched chains and rings like other organic compounds. A straight-chain alkane, a branched-chain alkane, and a cycloalkane are alkane examples of alkanes. Alkane molecules with straight and branched chains have a molecular formula of CnH2n+2, and those with cyclic chains are CnH2n.

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Groups and Alkyls

A carbon-hydrogen bond in an alkane molecule becomes a carbon-substituent bond when a substituent like halogen bonds to it. The process of methane reacting with chlorine forms chloromethane, which is a new compound. CH3 atoms are joined to chlorine atoms in the new compound.Substitution reaction

The term alkyl group refers to the removal of hydrogen from one bond in a diketone. This Alkyl group is also commonly represented by the letter R, as opposed to the letter X representing halogens. This reaction between methane and chlorine can be generalized as

Alkane substitution reaction

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Frequently Asked Questions (FAQs)

1. Give the first four Alkanes compounds?

The first four alkanes are methane (CH4),ethane(C2H6) propane(C3H8), butane (C4H10).

2. What is the classification of alkanes?

Alkanes consist of hydrocarbon atoms with only one bond. Alkanes are divided into three types: linear straight alkanes, branched alkanes and cyclic alkanes.

3. Does alkanes have functional groups?

A neutral alkane usually does not have a functional group but is composed of a component without one. Alkenes are functional groups composed of carbon-carbon double bonds.

4. What is the molecular formula of alkyne?

Alkanes are a class of hydrocarbons that consist solely of carbon (C) and hydrogen (H) atoms, connected exclusively by single covalent bonds (sigma bonds). They follow the general formula CₙH₂ₙ₊₂, where n is the number of carbon atoms.


5. What are Tricarbonyl Hydrocarbons?

Tricarbonyl hydrocarbons are known as alkynes. Their geometric and optical isomerisms are not visible. It is the easiest alkyne to produce, often called acetylene (HC≡CH or C2H2) shown to the right.

6. What is the general formula for alkanes?
The general formula for alkanes is CnH2n+2, where n represents the number of carbon atoms in the molecule. This formula applies to all straight-chain and branched alkanes.
7. What are isomers in the context of alkanes?
Isomers are molecules with the same molecular formula but different structural arrangements. In alkanes, structural isomers have the same number of carbon and hydrogen atoms but differ in how these atoms are connected. For example, butane and 2-methylpropane are isomers with the formula C4H10.
8. What is the difference between straight-chain and branched alkanes?
Straight-chain alkanes have all carbon atoms arranged in a linear sequence, while branched alkanes have carbon atoms that branch off from the main chain. For example, butane is a straight-chain alkane, while 2-methylpropane is a branched alkane with the same number of carbon atoms.
9. What is the significance of the C-C bond rotation in alkanes?
The C-C bond rotation in alkanes is significant because:
10. How does the reactivity of primary, secondary, and tertiary carbons in alkanes differ?
The reactivity of carbon atoms in alkanes differs based on their type:
11. How do the physical properties of alkanes change as the number of carbon atoms increases?
As the number of carbon atoms in alkanes increases:
12. How does branching affect the physical properties of alkanes?
Branching in alkanes generally:
13. How do intermolecular forces affect the properties of alkanes?
Intermolecular forces, specifically van der Waals forces, affect alkane properties by:
14. How do alkanes contribute to the greenhouse effect?
Alkanes, particularly methane (CH4), contribute to the greenhouse effect by trapping heat in the Earth's atmosphere. When released into the atmosphere, these molecules absorb and re-emit infrared radiation, leading to global warming. Methane is a particularly potent greenhouse gas, with a global warming potential about 25 times that of carbon dioxide over a 100-year period.
15. How do alkanes contribute to air pollution?
Alkanes contribute to air pollution in several ways:
16. What are alkanes and how are they defined in organic chemistry?
Alkanes are a class of hydrocarbons that consist of only carbon and hydrogen atoms connected by single bonds. They are defined as saturated hydrocarbons, meaning they have the maximum number of hydrogen atoms bonded to each carbon atom.
17. Why are alkanes considered saturated hydrocarbons?
Alkanes are considered saturated hydrocarbons because each carbon atom in the molecule is bonded to the maximum number of hydrogen atoms possible. This means there are no double or triple bonds between carbon atoms, only single bonds.
18. How do alkanes react with oxygen, and what is this process called?
Alkanes react with oxygen in a process called combustion. This is an exothermic reaction where the alkane combines with oxygen to produce carbon dioxide and water, releasing heat and light. The general equation is:
19. How do alkanes differ from cycloalkanes?
Alkanes and cycloalkanes differ in the following ways:
20. Why are alkanes considered relatively unreactive compared to other hydrocarbons?
Alkanes are considered relatively unreactive because they contain only strong, stable carbon-carbon and carbon-hydrogen single bonds. These bonds are not easily broken or rearranged, making alkanes less reactive than hydrocarbons with double or triple bonds.
21. What is the significance of the carbon-carbon bond length in alkanes?
The carbon-carbon bond length in alkanes is significant because:
22. How does the concept of hybridization apply to alkanes?
In alkanes, carbon atoms undergo sp3 hybridization:
23. What is the importance of the carbon-hydrogen bond in alkanes?
The carbon-hydrogen bond in alkanes is important because:
24. What is the concept of homologous series in relation to alkanes?
The homologous series of alkanes refers to:
25. What is the importance of alkanes in the production of polymers?
Alkanes are important in polymer production because:
26. What is the IUPAC naming system for alkanes?
The IUPAC (International Union of Pure and Applied Chemistry) naming system for alkanes follows these basic rules:
27. What is the significance of alkanes in the petroleum industry?
Alkanes are significant in the petroleum industry because:
28. How does the reactivity of alkanes compare to alkenes and alkynes?
Alkanes are generally less reactive than alkenes and alkynes because:
29. What is meant by the term "cracking" in relation to alkanes?
Cracking is a process used in the petroleum industry to break down larger alkane molecules into smaller, more useful hydrocarbons. This is typically done using heat, pressure, and sometimes catalysts. Cracking helps produce more valuable products like gasoline from heavier, less useful hydrocarbons.
30. What is the role of alkanes in biological systems?
Alkanes play several roles in biological systems:
31. What is the relationship between alkanes and fossil fuels?
Alkanes and fossil fuels are closely related:
32. How do alkanes participate in free radical reactions?
Alkanes participate in free radical reactions through the following steps:
33. How do alkanes interact with water, and why?
Alkanes interact poorly with water due to their non-polar nature:
34. How do alkanes behave under extreme pressures and temperatures?
Under extreme conditions, alkanes exhibit interesting behaviors:
35. What is the role of catalysts in alkane reactions?
Catalysts play important roles in alkane reactions:
36. How do alkanes contribute to the octane rating of gasoline?
Alkanes contribute to the octane rating of gasoline in the following ways:
37. What is the significance of the carbon skeleton in alkanes?
The carbon skeleton in alkanes is significant because:
38. How do alkanes participate in substitution reactions?
Alkanes participate in substitution reactions as follows:
39. What is the relationship between alkanes and alkyl groups?
Alkanes and alkyl groups are related in the following ways:
40. How do alkanes influence the properties of mixtures like crude oil?
Alkanes influence the properties of mixtures like crude oil by:
41. What is the importance of conformational analysis in alkanes?
Conformational analysis in alkanes is important because:
42. How do alkanes interact with different types of solvents?
Alkanes interact with solvents in the following ways:
43. What is the significance of alkanes in the study of organic reaction mechanisms?
Alkanes are significant in the study of organic reaction mechanisms because:

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Questions related to

Have a question related to ?

Question : Which of the following pair of compound – general formula is correct?
I. Alkenes – CnH2n
II. Alkanes – CnH2n-1

Option 1: Only II

Option 2: Only I

Option 3: Neither I nor II

Option 4: Both I and II

Correct Answer: Only I


Solution : The correct answer is Only I

Alkenes are hydrocarbons with at least one carbon-carbon double bond, whether they are branched or unbranched. There is at least one carbon-to-carbon double bond in every alkene. CnH2n is the general formula for alkenes. A family of compounds known as cycloalkanes is made up of carbon atoms joined in a circle. CnH2n+2 is the general formula for cycloalkanes.

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Team Careers360 24 January,2024

Question : In organic chemistry, which of the following is an empirical rule used to predict the regioselectivity of electrophilic addition reactions of alkanes and alkynes?

Option 1: Cornforth’s rule

Option 2: Bredt’s rule

Option 3: Markovnikov’s rule

Option 4: Baldwin’s rule

Correct Answer: Markovnikov’s rule


Solution : The correct answer is Markovnikov’s rule.

Certain chemical addition reactions can be described by Markovnikov's rule, commonly referred to as Markovnikov's rule. As per this rule, the carbon (C) atom with fewer hydrogen atoms is bound by the nucleophilic X-, whereas the carbon atom with more hydrogen atoms attached to it is bound by the proton.

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