Alkanes are insoluble in water and less dense than water. Carbon chains of varying length have been observed in organic compounds having the same general formula. The iupac names of the first five members of this series are given in the following table. The second alkane is ethane, which has two carbon atoms. An homologous series is a group of compounds with similar structural features that can be represented by a general formula whose members differ by one ch 2 unit you can think of an homologous series as a family or group of compounds, whose chemical behaviour is very similar and whose physical properties show trends when ascending the members of the group in terms of. The compounds are named as for the alkanes, but with the ending, ene instead of ane. It makes use of 3d modelling in considering how the general formula of an. The series of carbon compounds in which two successive compounds differ by ch 2 unit is called homologous series. Explain the properties within and between the homologous.
A homologous series is a group of chemicals which have similar chemical properties. For example, methane, ethane, propane, butane, etc. It can be formed many ways of which some are i catalytic cracking in this process large alkanes are. Hence the first 10 molecules in the homologous series of linear alkanes may be listed as follows below, right. It makes use of 3d modelling in considering how the general formula of an homologous series is used to generate the molecular. Alkane, normal alkane, cycloalkane, homologous series. A series of compounds in which successive members differ from one another by a ch 2 unit is called a homologous series. This means that they have similar chemical properties to each other and they have trends in physical properties.
In the field of organic chemistry, a homologous series is a sequence of compounds with the same functional group and similar chemical properties in which the members of the series can be branched or unbranched. The homologous series of straightchained alkanes begins methane ch4, ethane c2h6. The formation of crude oil finding crude oil drilling for crude oil part 1 drilling for crude oil part 2. Predict and explain the trends in boiling points of members of a homologous series. Octane is the eighth member of the alkane homologous series. All the families of organic compounds exist as a homologous series a series having a difference of ch2 unit between two consecutive members the main homologous series es are alkanes, alkenes.
A group of compounds such as the unbranched alkanes that differ from one another by successive introduction of ch 2 groups constitute a homologous series. Covalent bonds are formed when atoms share pair of electrons. Same general formula allow a named homologous series with its general formulachemically similarsame chemical reactions same functional grouptrend in physical properties eg inc bp as mr increasesmolecules increase by ch2mr. Ib chemistryorganic chemistry wikibooks, open books for. This means that they have similar chemical properties to each other and they have trends in physical. The homologous series of straightchained alkanes begins withmethanech 4,ethanec 2 h 6,propanec 3 h 8,butanec 4 h 10, andpentanec 5 h 12. How are alkanes, alkenes, and alkynes homologous series. Predict and explain the trends in boiling points of members of a homologous series within a homolgous series the intermolecular forces are the same. In that series, successive members differ in mass by an extramethylene bridgech 2 unit inserted in the chain. The simplest alkane, methane, has one carbon atom and a molecular formula of ch 4. That is, the more carbons, the higher the temperature. In the homologous series of alkanes, what is the molecular formula for the member just above c 8 h 18 use the general formula for alkanes to write the molecular formula of the alkane with 12 carbon atoms. The melting and boiling points of alkenes follow the same trends as those of alkanes, for the same reasons.
Such organic compounds that vary from one another by a repeating unit and have the same. A homologation reaction is a chemical process that converts one member of a homologous series to the next member. Organic chemistry alcohols alcohols form stronger intramolecular and intermolecular hydrogen bonds. Such organic compounds that vary from one another by a repeating unit and have the same general formula form a series of compounds. Explain the properties within and between the homologous series of alcohols with reference to the intermolecular and intramolecular bonding present. Compounds within a homologous series typically have a fixed set of functional groups that gives them similar chemical and physical properties. Homologous series is a series where in the hydrogen atom is replaced by the same functional group in multiple carbon compounds.
Explanation of solution an alkane is defined as hydrocarbon in which each carbon atom forms a. Methane ethane propane if one of the hydrogen atoms is removed what is left is known as an alkyl radical r e. The general formula for the homologous series of alkenes is cnh2n where n is the number of carbon atoms. In the homologous series of alkanes, what is the molecular formula for the. Natures chemistry homologous series national 5 chemistry. The ch 2 group is nonpolar hydrophobic and this increases the percentage of the molecule that is unattractive to water. Alevel chemistryocrchains, energy and resourcesbasic. Homologous series is a series of compounds with similar chemical properties and same functional group differing from the successive member by ch 2. Homologous series of alkanes, alkenes and alkynes with. The alkane series is an organic homologous series consisting of repeating ch2 units. In chemistry, a homologous series is a group of compounds that share the same basic chemical makeup, but differ in the number of iterations of a certain aspect of their structure.
With their repeated ch 2 units, the alkanes constitute a homologous series of organic compounds in which the members differ in molecular mass by multiples of 14. Alkanes are organic compounds that consist of singlebonded carbon and hydrogen atoms. The alkanes, alkenes and cycloalkanes are examples of homologous series. Significance and properties of the homologous series gulpmatrix.
Identify and name simple straightchain alkanes given formulas and write formulas. Nov 22, 2019 a homologous series is a series of compounds with the same general formula, usually varying by a single parameter such as the length of a carbon chain. Organic compounds consequently tend to be less soluble as an homologous series is ascended. Alkanes are virtually insoluble in water, but dissolve in organic solvents. The carbon atom can form bonds with other atoms like hydrogen, oxygen, nitrogen, etc. The graph above plots the melting point temperatures of the first 32 alkanes as squares. Methane ch 4 ethane ch 3 ch 3 propane ch 3 ch 2 ch 3 butane ch 3 ch 2 ch 2 ch 3 a i state what is meant by the term hydrocarbon. The resulting molecules can contain from one to millions of carbon atoms. For example, the first alkane is methane, which has a formula of ch4.
The independent variables are the molar mass of the compound and the identity and position of the functional group a control variable is that i will only look at. The simplest series of compounds in organic chemistry is the alkanes. This makes them less volatile than alkanes and alkenes. Alkanes formula, definition, structure, properties, videos. Cycloalkanes have one or more rings of carbon atoms. Because alkenes are hydrocarbons with at least one carboncarbon double bond the alkene homologous series starts at ethene c 2 h 4. This is not something that i was expecting at first and i cannot easily explain the fact that melting temperatures of aldehydes, ketones and alcohols remain significantly above the melting temperature of the alkane of similar molar mass.
Jul 27, 2015 deltastep is a social initiative by graduates of iimahmedabad, iimbangalore, iitkharagpur, isikolkata, columbia university usa, ntu singapore and other leading institutes. A homologous series in organic chemistry is a group of organic compounds compounds that contain c atoms that differ from each other by one methylene ch 2 group. The successive members vary from each other by a ch 2 unit. Explain the properties within and between the homologous series of alcohols with reference to the intermolecular and intramolecular bonding present organic chemistry alcohols alcohols form stronger intramolecular and intermolecular hydrogen bonds which is the reason of their elevated boiling points. A homologous series is a series of carbon compounds that have different numbers of carbon atoms but contain the same functional group. Alkanes are comprised of a series of compounds that contain carbon and hydrogen atoms with single covalent bonds. The lower members of the homologous series are gases at room temperature. A homologous series is a group of chemicals which have similar chemical properties and can be represented by a general formula.
The difference between each member of an homologous series is one ch 2 unit. The first four straightchain alkanes are shown below. Hence, it can link to other carbon atoms forming large molecules. Homologous series are referenced frequently in organic chemistry, where compounds can differ by the length of their carbon chain. It is important that you commit to memory the names of the first 10 straightchain alkanes i. Mar 20, 2014 homologous series the alkanes form a series of compounds all with the same general formula e. The liquid alkanes are good solvents for many other covalent compounds. Give two characteristics, other than having the same general formula, of members of an homologous series. A homologous series is formed by the addition of a. We shall study this series to illustrate what a homologous series means. In a homologous series there is a gradual increase in boiling point as the number of carbon atoms increases. The alkenes form a homologous series with general formula c n h 2n for cycloalkenes it would be c n h 2n2. Alkanes are generally unreactive toward laboratory acids, bases, oxidizing agents, and reducing agents. The alkanes comprise a series of compounds that are composed of carbon and hydrogen atoms with single covalent bonds.
The same thing can be observed in case of alkenes in which the first member is ethene and the successive members are c 3 h 6, c 4 h. Ib chemistryorganic chemistry wikibooks, open books for an. Each alkane has two hydrogen atoms in addition to its ch2 units. In the field of organic chemistry, a homologous series is a sequence of compounds with the. Homologous series the alkanes form a series of compounds all with the same general formula e. The homologous series of straightchained alkanes begins methane ch 4, ethane c 2 h 6, propane c 3 h 8, butane c 4 h 10, and pentane c 5 h 12.
Alkanes alkanes and alkenes gcse chemistry single science. A homologous series is a series of compounds with the same general formula, usually varying by a single parameter such as the length of a carbon chain. T he numerous organic compounds can be grouped into a comparatively small number of series or families of compounds known as homologous series. Most of the hydrocarbons in crude oil are hydrocarbons called alkanes. Beginning with fivecarbon chains, the names of unbranched alkanes consist of a latin or greek stem corresponding to the number of carbons in the chain followed by the suffix ane. Hydrocarbons are chain molecules of varying lengths made from hydrogen and carbon atoms only, joined together by covalent bonds. Alkanes and halogenated hydrocarbons through chapter 15 organic acids and bases and some of their derivatives, we survey organic chemistry by. What follows applies equally to alkanes and cycloalkanes. Such a family of compounds is known as a homologous.
She writes one formula with all five carbon atoms in a horizontal line and the other with four carbon atoms in a line. The alkanes form an homologous series of hydrocarbons. A brief description of the relationship between alkane, cycloalkane, and homologous series is to be determined. Homologous series of alkanes, alkenes and alkynes with examples. For example in ch 4 and c 2 h 6, the difference is ch 2 unit and the difference between c 2 h 6 and c 3 h 8 is also ch 2 unit. When a molecular substance dissolves in water, you have to. This video explains and illustrates what homologous series are. Alkanes react with halogens by substituting one or more halogen atoms for hydrogen atoms to form halogenated hydrocarbons. But, alkanes are hydrocarbons, meaning that there are only hydrogen and carbon atoms. A student is asked to write structural formulas for two different hydrocarbons having the molecular formula c 5 h 12.
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