Inspection of the graph shows there is a direct relationship between the number of carbons in an alkane and its meltingboiling point temperature. The carbon atom can form bonds with other atoms like hydrogen, oxygen, nitrogen, etc. T he numerous organic compounds can be grouped into a comparatively small number of series or families of compounds known as homologous series. The compounds are named as for the alkanes, but with the ending, ene instead of ane. Homologous series is a series of compounds with similar chemical properties and same functional group differing from the successive member by ch 2. It makes use of 3d modelling in considering how the general formula of an homologous series is used to generate the molecular. Each alkane has two hydrogen atoms in addition to its ch2 units. In chemistry, a homologous series is a series of organic compounds with a similar general formula, possessing similar chemical properties due to the presence of the same functional group, and. 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.
Hence, it can link to other carbon atoms forming large molecules. 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. This makes them less volatile than alkanes and alkenes. The melting and boiling points of alkenes follow the same trends as those of alkanes, for the same reasons.
But, alkanes are hydrocarbons, meaning that there are only hydrogen and carbon atoms. Octane is the eighth member of the alkane homologous series. A brief description of the relationship between alkane, cycloalkane, and homologous series is to be determined. Alkane, normal alkane, cycloalkane, 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. This means that they have similar chemical properties to each other and they have trends in physical. Give two characteristics, other than having the same general formula, of members of an homologous series. Homologous series are referenced frequently in organic chemistry, where compounds can differ by the length of their carbon chain. The second alkane is ethane, which has two carbon atoms. There is another classification based on homologous series. 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. 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. 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 successive members vary from each other by a ch 2 unit. The alkane series is an organic homologous series consisting of repeating ch2 units. Alkanes react with halogens by substituting one or more halogen atoms for hydrogen atoms to form halogenated hydrocarbons. 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. The alkanes, alkenes and cycloalkanes are examples of homologous series. The simplest alkane, methane, has one carbon atom and a molecular formula of ch 4. Alkanes are organic compounds that consist of singlebonded carbon and hydrogen atoms. In the field of organic chemistry, a homologous series is a sequence of compounds with the. Ib chemistryorganic chemistry wikibooks, open books for. A series of compounds in which successive members differ from one another by a ch 2 unit is called a homologous series.
Homologous series are referenced frequently in organic chemistry, where compounds can. Ib chemistryorganic chemistry wikibooks, open books for an. A homologous series is a group of chemicals which have similar chemical properties and can be represented by a general formula. 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. It can be formed many ways of which some are i catalytic cracking in this process large alkanes are. The alkanes form an homologous series of hydrocarbons. A homologation reaction is a chemical process that converts one member of a homologous series to the next member. A student is asked to write structural formulas for two different hydrocarbons having the molecular formula c 5 h 12. Such organic compounds that vary from one another by a repeating unit and have the same general formula form a series of compounds.
What follows applies equally to alkanes and cycloalkanes. Alkanes formula, definition, structure, properties, videos. Methane ethane propane if one of the hydrogen atoms is removed what is left is known as an alkyl radical r e. Alevel chemistryocrchains, energy and resourcesbasic. 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. 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. For example, methane, ethane, propane, butane, etc. What are the physical and chemical properties of homologous. Predict and explain the trends in boiling points of members of a homologous series. For example, the first alkane is methane, which has a formula of ch4.
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. The alkanes comprise a series of compounds that are composed of carbon and hydrogen atoms with single covalent bonds. The homologous series of straightchained alkanes begins methane ch4, ethane c2h6. 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. A homologous series is a series of carbon compounds that have different numbers of carbon atoms but contain the same functional group. We shall study this series to illustrate what a homologous series means.
This can be the length of a carbon chain, for example in the straightchained alkanes paraffins, or it could be the number of monomers in a homopolymer such as amylose. Most of the hydrocarbons in crude oil are hydrocarbons called alkanes. Carbon chains of varying length have been observed in organic compounds having the same general formula. 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. Cycloalkanes have one or more rings of carbon atoms. Homologous series of alkanes, alkenes and alkynes with examples. It is important that you commit to memory the names of the first 10 straightchain alkanes i.
In a homologous series there is a gradual increase in boiling point as the number of carbon atoms increases. The simplest examples of this class consist of a single, unsubstituted carbon ring, and these form a homologous series similar to the unbranched alkanes. The alkenes form a homologous series with general formula c n h 2n for cycloalkenes it would be c n h 2n2. Compounds within a homologous series typically have a fixed set of functional groups that gives them similar chemical and physical properties. 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. The lower members of the homologous series are gases at room temperature. The series of carbon compounds in which two successive compounds differ by ch 2 unit is called homologous series. This video explains and illustrates what homologous series are. In the homologous series of alkanes, what is the molecular formula for the. Homologous series of alkanes, alkenes and alkynes with. The difference between each member of an homologous series is one ch 2 unit. The liquid alkanes are good solvents for many other covalent compounds. A homologous series is a group of chemicals which have similar chemical properties.
Covalent bonds are formed when atoms share pair of electrons. 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. This means that they have similar chemical properties to each other and they have trends in physical properties. Homologous series is a series where in the hydrogen atom is replaced by the same functional group in multiple carbon compounds. It deals with their formulae and isomerism, their physical properties, and an introduction to their chemical reactivity. Alkanes and halogenated hydrocarbons through chapter 15 organic acids and bases and some of their derivatives, we survey organic chemistry by. The iupac names of the first five members of this series are given in the following table. 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. Significance and properties of the homologous series gulpmatrix.
The resulting molecules can contain from one to millions of carbon atoms. 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. Organic chemistry alcohols alcohols form stronger intramolecular and intermolecular hydrogen bonds. The ch 2 group is nonpolar hydrophobic and this increases the percentage of the molecule that is unattractive to water. Thus themolecular massof each member differs by 14atomic massunits. Significance and properties of the homologous series. The general formula for the homologous series of alkenes is cnh2n where n is the number of carbon atoms.
The formation of crude oil finding crude oil drilling for crude oil part 1 drilling for crude oil part 2. So, none of the hydrogen atoms are being replaced by a functional group. Organic compounds consequently tend to be less soluble as an homologous series is ascended. How are alkanes, alkenes, and alkynes homologous series. Jul 27, 2015 deltastep is a social initiative by graduates of iimahmedabad, iimbangalore, iitkharagpur, isikolkata, columbia university usa, ntu singapore and other leading institutes. Identify and name simple straightchain alkanes given formulas and write formulas.
Such a family of compounds is known as a homologous. 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. Homologous series the alkanes form a series of compounds all with the same general formula e. Alkanes are insoluble in water and less dense than water. She writes one formula with all five carbon atoms in a horizontal line and the other with four carbon atoms in a line. When a molecular substance dissolves in water, you have to. 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 serieses are alkanes, alkenes. Hydrocarbons are chain molecules of varying lengths made from hydrogen and carbon atoms only, joined together by covalent bonds. A homologous series is formed by the addition of a. Explain the properties within and between the homologous. The simplest series of compounds in organic chemistry is the alkanes. That is, the more carbons, the higher the temperature.
The alkanes are a homologous series of hydrocarbons. Explanation of solution an alkane is defined as hydrocarbon in which each carbon atom forms a. Alkanes alkanes and alkenes gcse chemistry single science. Mar 20, 2014 homologous series the alkanes form a series of compounds all with the same general formula e. 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.
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. Alkanes are generally unreactive toward laboratory acids, bases, oxidizing agents, and reducing agents. 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. In that series, successive members differ in mass by an extramethylene bridgech 2 unit inserted in the chain. Natures chemistry homologous series national 5 chemistry. Alkanes are comprised of a series of compounds that contain carbon and hydrogen atoms with single covalent bonds. Alkanes are virtually insoluble in water, but dissolve in organic solvents. 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. The first four straightchain alkanes are shown below. The graph above plots the melting point temperatures of the first 32 alkanes as squares. Such organic compounds that vary from one another by a repeating unit and have the same.
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