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. They have similar chemical properties because chemical properties depends on bonding. The chainis the line of carbon atoms joined together. Thus, the homologous series of alkanes continues with pentane, hexane, heptane, octane, nonane, decane, and so on. Functional groups and homologous series question 2. In that series, successive members differ in mass by an extra methylene bridge ch 2 unit inserted in the chain. In first year organic chemistry, the first ten names of the homologous series are usually all that need to be memorized. A homologous series is a group or family of organic compounds that has certain characteristics. We propose that propane studied more extensively here, beyond methane, is a surrogate of the reactivity of the alkane homologous series but other. Homologous series of alkanes, alkenes and alkynes with.
Using their condensed structural formulas, rank the homologous series for a set of alkanes by their boiling point. A homologous series is a group of chemicals which have similar chemical properties and can be represented by a general formula. The first four alkanes in the homologous series retain their original names. Some examples of homologous series are shown in the following table. The compounds are named as for the alkanes, but with the ending, ene instead of ane. Some important series of aliphatic compounds are listed below. Made for lower ability students but can be easily adapted for higher ability students. The simplest alkane, methane, has one carbon atom and a molecular formula of ch 4. Significance and properties of the homologous series.
It can be formed many ways of which some are i catalytic cracking in this process large alkanes are. The next alkanes are c 2 h 6 n 2, c 3 h 8 n 3, and so on so forth. 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. 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. As the number of carbons increases in an homologous series the melting point generally. So, none of the hydrogen atoms are being replaced by a functional group. It makes use of 3d modelling in considering how the general formula of an homologous series is used to generate the molecular. Functional groups and homologous series question 1. The alkanes, alkenes and cycloalkanes are examples of homologous series. The principle of homology allows us to write a general formula for alkanes. Carbon chains of varying length have been observed in organic compounds having the same general formula. This means that they have similar chemical properties to each other and they have trends in physical properties. A brief look at cracking alkanes in the oil industry.
Alkanes alkanes and alkenes gcse chemistry single science. Consider structures of first five members of the series. If we examine the unbranched alkanes, we notice that each alkane differs from the preceding alkane by one ch 2 group. 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. With a proper surrogate, the universality of the homologous series holds indeed valid as expected, i. Use the general formula for alkanes to write the molecular formula of the alkane with 12 carbon atoms. Oct 24, 2012 homologous series is a series where in the hydrogen atom is replaced by the same functional group in multiple carbon compounds. Homologous series is a series of compounds with similar chemical properties and same functional group differing from the successive member. Significance and properties of the homologous series gulpmatrix. 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. Homologous series examples, answers, activities, experiment.
The alkanes comprise a series of compounds that are composed of carbon and hydrogen atoms with single covalent bonds. Methane belongs to the homologous series of alkane. Natures chemistry homologous series national 5 chemistry. 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. Chemicals in the same homologous series will show a gradual variation in one property eg. Homologous series, any of numerous groups of chemical compounds in each of which the difference between successive members is a simple structural unit. 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. A homologous series is a group of chemicals which have similar chemical properties.
After these the names are formed by adding the ending ane to the greek word for the number of carbon atoms in the molecule. This means that they have similar chemical properties to each other and they have trends in physical. The general formula for the homologous series of alkenes is cnh2n where n is the number of carbon atoms. At room temperature 25c and 1 atm pressure, the first four members of the homologous series of unbranched alkanes are gases, the c 5 c 17 unbranched alkanes pentane to heptadecane are liquids, and the unbranched alkanes with 18 and more carbon atoms are solids. Each succeeding formula incorporates one carbon atom and two hydrogen atoms more than the previous formula.
The successive members vary from each other by a ch 2 unit. Because alkanes only contain carboncarbon single bonds and carbonhydrogen bonds they are all going to behave in the same way. Remembering that there must be one bond per hydrogen and four bonds per carbon, one can see that for the three simplest alkanes, there is only one configuration, or molecular structure that can exist, as shown in figure 37. Homologous series a homologous series is a group of compounds with similar characteristics and the same general formula. Many homologous series can be regarded as being derived from the alkanes by the substitution of one or more of the hydrogen atoms by other elements or groups. 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 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 alkanes are a homologous series of hydrocarbons. Including activity building structures using the molymods also includes a simple worksheet. Mcq for 25 marks and theory for 15 marks with answer key both word and pdf format is also included for concept check. Aug 20, 2018 what do you mean by homologous series.
In the homologous series of alkanes, what is the molecular formula for the member just above c 8 h 18. Hydrocarbons are chain molecules of varying lengths made from. The homologous series of straightchained alkanes begins methane ch4, ethane c2h6, propane c3h8, butane c4h10, and pentane c5h12. Homologous series of nalkanes c 19 c 35, fatty acids c 12 c 32 and nalcohols c 8 c 30 in atmospheric aerosols from central alaska. Molecular distributions, seasonality and source indices. Alkanes, alkenes, alcohols, carboxylic acids and esters belong to different homologous series.
Mar 03, 2018 follows edexcel 91 combined science gcse powerpoint about alkanes, alkenes and alcohols. Homologous series have the same general formula with the neighbouring members of the series differing by ch2. Homologous series homologous series characteristics. Oct 30, 2014 this video explains and illustrates what homologous series are. At the boiling point of a substance, the intermolecular forces of attraction must be overcome to convert it from a liquid to a solid. 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. Properties of alkanes organic chemistry quiz quizizz. Pdf homologous series of nalkanes c 19 c 35, fatty. Hydrocarbons are chain molecules of varying lengths made from hydrogen and carbon atoms only, joined together by covalent bonds. Notice, there is a steady difference of number of carbon and hydrogen atoms from lower alkanes to higher alkanes, the constant difference between successive members being ch 2. Organic compounds are grouped into different homologous series. There are a number of homologous series in organic compounds. Butane, for example, is ch 3 ch 2 2 ch 3 and pentane is ch 3 ch 2 3 ch 3.
Rank these alkanes from highest to lowest boiling points 1. Structures and names of alkanes chemistry libretexts. Homologous series of n alkanes c 19 c 35, fatty acids c 12 c 32 and nalcohols c 8 c 30 in atmospheric aerosols from central alaska. Electrochemical and photoelectrochemical properties of monoaza15crown ether linked cyanine dyes. An introduction to the alkanes including cycloalkanes and their physical properties. Such a family of compounds is known as a homologous. It makes use of 3d modelling in considering how the general formula of an. But, alkanes are hydrocarbons, meaning that there are only hydrogen and carbon atoms. Any family of compounds in which adjacent members differ from each other by a definite factor here a ch 2 group is called a homologous seriesany family of. 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. Such series are most common among organic compounds, the structural difference being a methylene group, as in the paraffin hydrocarbons, or alkanes. Homologous series means that the series has the same general formula and the compounds have similar properties and structure, differing only in the number of ch 2 units in the chain. The chemical properties between members of the same homologous series are similar, but the physical properties change gradually as the size of the compounds grow.
Jun 12, 2017 order in homologous series photograph shows the first members of various homologous series. Masaaki satou, hirofumi nemoto, susumu yokoyama, and yuzo sanada. The organisation of organic compounds into the various different homologous series makes the study of organic chemistry more systematic, orderly and effective. Alkanes including methane are the simplest carbonbased homologous series.
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 and structural isomerism this resource is based on igcse chemistry 0620 syllabus and id ideal for home learning and class room teaching. Dec, 2011 the boiling points for a set of compounds in a homologous series can be qualitatively predicted using intermolecular force strengths. Homologous series of alkanes, alkenes and alkynes with examples. Mcq for 25 marks and theory for 15 marks with answer key both word and pdf format is. What is similar about members of the same homologous series. The combustion of alkanes, including incomplete combustion. Covalent bonds are formed when atoms share pair of electrons. The univalent group which is formed from an alkane by the loss of a hydrogen atom is known as the alkyl group.