Writing the formulas for simple alkanes, alkenes and alkynes is as simple as determining how many carbons are in the formula and then putting that number into the generic formula for that hydrocarbon. Each degree of unsaturation represents a double bond or a ring. Such organic compounds that vary from one another by a repeating unit and have the same. Chem alkanes and alkenes chemistry organic chemistry.
Alkynes are traditionally known as acetylenes, although the name acetylene also refers specifically to c 2 h 2, known formally as ethyne using iupac nomenclature. The words alkene and olefin are often used interchangeably. General formula of organic compound cbse icse duration. The simplest acyclic alkynes with only one triple bond and no other functional groups form a homologous series with the general chemical formula c n h 2n. A homologous series is a family of organic compounds with similar chemical properties. The general formula for the homologous series of alkenes is cnh2n where n is the number of carbon atoms.
This group of compounds is a homologous series with the general molecular formula of c n h 2 n 2, where n equals any integer greater than one. For example, methane, ethane, and propane are part of a homologous series. Homologous series are not unique to organic chemistry. Mar 14, 2020 for unsaturated hydrocarbons, refine the classification by indicating whether the compound is an alkene, alkyne, or arene. Alkenes are unsaturated hydrocarbons with one double bond rccr. Each successive member in such a series differs in its molecular formula by the addition of a ch 2 group and in its relative molecular mass by an. Homologous series of alkanes, alkenes and alkynes with examples. They are from a homologous series with the general formula c n h 2n. The words alkene and olefin are often used interchangeably see nomenclature section below. Aug 12, 2019 the principle of homology allows us to write a general formula for alkanes.
Gce study buddy the best o level revision resource. How are alkanes, alkenes, and alkynes homologous series since. Using a mnemonic can make learning the names easier. A homologous series of hydrocarbons that contains double carbon bonds. A series of compounds in which successive members differ from one another by a ch 2 unit is called a homologous series. Saturated hydrocarbons alkanes are the simplest of the hydrocarbon species. Such a family of compounds is known as a homologous. Each successive member differs by a ch2 group or by a mass of 14 amu. 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.
Is the special group of atoms available in homologous series compounds which is responsible for the chemical properties of the compound. The general formula for alkenes are c n h 2n, where n is the number of carbons in the alkene. All the members of a series can be represented by the same general formula. The name homologous series is also often used for any collection of compounds that have similar structures or include the same functional group, such as the general alkanes straight and branched. Homologous series have the same general formula with the neighbouring members of the series differing by ch 2. Titanium, vanadium, and molybdenum oxides all form homologous series e. The alkanes, alkenes and cycloalkanes are examples of homologous series. The compounds of the homologous series have some characteristics they are as follows. Acyclic alkenes, with only one double bond and no other functional groups, known as monoenes, form a homologous series of hydrocarbons with the general formula c n h 2n. Due to the general structure of alkenes, they always have twice as many hydrogens as carbons. Those containing triple bonds are called alkynes and have general formula c n h 2n2. 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 sheer scale of organic chemistry means that it is important to categorise compounds with similarities in order to make sense of the vast number of organic compounds possible.
Acyclic alkenes, with only one double bond and no other functional groups, known as monoenes, form a homologous series of hydrocarbons with the general formula cnh2n. Which hydrocarbon is a member of the series with the general formula cnh2n2. Any of a series of unsaturated, aliphatic hydrocarbons with a carboncarbon double bond, having the general formula cnh2n. However, if the members cannot be arranged in a linear order by a single parameter, the collection. These atoms or groups attached are known as functional groups and the series formed are all homologous series. Ethene is an important raw material for the petrochemical industry. The simplest alkene, ethylene, with the iupac name ethene, is the organic compound produced. Nov 05, 20 learn the basics of alkanes and alkenes. What are the general formulas for alkane, alkene, alkyne, alkyl, aldehyde, ketone, cycloalkane.
Nature of element all the members of series have same type of elements. The names, molecular formula and the structural formula of the first eight alkanes must be learned. Alkenes are organic molecules that form an homologous series with the general. A homologous series is a group of chemicals which have similar chemical properties and can be represented by a general formula. Due to presence of strong sigma bond alkanes are chemically less reactive and also called paraffins less ability to co. The general formula for the alkenes is c nh 2n, where n is the number of carbon atoms in the molecule.
The smallest alkeneethenehas two c atoms and is also known by its common name ethylene and the. 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 carboncarbon double bond is the functional group of the alkene family. Those with double bond are called alkenes and have the general formula c n h 2n assuming noncyclic structures. The general formula for the alkene family is c n h 2n, where n 2, 3, 4, alkenes are unsaturated hydrocarbons.
Each member of the series differs from the next by a. Members of a homologous series have similar chemical reactions. Categorisation relies on similarities between and within structures, giving rise to the concept of homologous series. Predict the molecular formula of decene and explain your answer. Start studying organic chemistry alkanes, alkenes, alcohols and carboxylic acid formulas. For example, an alkane with eight carbon atoms has the molecular formula c 8 h 2. They also have a similar trend in physical properties. Occurrence in nature, methane is formed by the microbial activity of. Therefore, the homologous series is a family of organic compound that is made out of members with common functional group, common chemical properties, and consecutive members are differ by one carbon atom and two hydrogen atom, namely, ch 2. Molecular formula molecular formula of different members of a homologous series differs from previous and next member by ch 2.
The first four alkanes in the homologous series retain their original names. Unsaturated hydrocarbons have double andor triple bonds between carbon atoms. The compounds are named as for the alkanes, but with the ending, ene instead of ane. They are composed entirely of single bonds and are saturated with hydrogen. In which group could the hydrocarbons all belong to the same homologous series. Carbon chains of varying length have been observed in organic compounds having the same general formula. Alkenes have the formula c n h 2n and alkynes use the formula c n h 2n2. What are the characteristics of homologous series answers. The simplest molecule in the alkene series is ethene, more commonly known as ethylene c 2 h 4. Jan 24, 2018 the alkenes are the unsaturated hydrocarbons that contain one double bond.
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. Alkenes have two hydrogen atoms fewer than the corresponding alkane. The name homologous series is also often used for any collection of compounds that have similar structures or include the same functional group, such as the general alkanes straight and branched, the alkenes olefins, the carbohydrates, etc. Significance and properties of the homologous series gulpmatrix.
Functional group all the members of homologous series contain same functional group. Homologous series of alkanes, alkenes and alkynes with. Structures and names of alkanes chemistry libretexts. Jun 15, 2017 what is the general formula for an alkene. Features include a general formula and neighbouring members differing by ch2, with similar chemical properties and with a gradation in physical properties. The number of carbons continuously bonded together is an important structural feature and is described using the homologous series. The general formula for the homologous series of alkenes is c n h 2n where n is the number of carbon atoms. Learn vocabulary, terms, and more with flashcards, games, and other study tools. Learn homologous series with free interactive flashcards. In organic chemistry, an alkyne is an unsaturated hydrocarbon containing at least one carboncarbon triple bond. Because alkenes are hydrocarbons with at least one carboncarbon double bond the alkene homologous series starts at ethene c 2 h 4. Which type of bond occurs in a saturated hydrocarbon molecule. Organic chemistry nomenclature naming functional groups 1 answer.
In case of alkanes, there is no functional group but thats not necessary for a homologous series. The alkenes comprise a series of compounds that are composed of carbon and hydrogen atoms with at least one double bond in the carbon chain. In organic chemistry, an alkene is an unsaturated hydrocarbon that contains a carboncarbon double bond. Alkenes have fewer hydrogens than alkanes and their general formula is cnh2n. The valency of a single carbon atom is satisfied by four hydrogen atoms which form single covalent bonds. Since alkenes contain double carbon bonds, they are unsaturated hydrocarbons. Oct 24, 2012 a homologous series is a series in which every compound has same general formula and have sam chemical properties followed by same functional groupif any. Molecular and structural formulas the alkynes comprise a series of carbon. It is important that you commit to memory the names of the first 10 straightchain alkanes i. Homologous series is a series of compounds with similar chemical properties and same functional group differing from the successive member by ch 2. In organic chemistry carbon chemistry, a homologous series refers to a family of compounds that. Alkenes have a general formula of cnh2n, where n may equal any number larger than one.
Although there is only one alkene with the formula c 2 h 4 ethene and only one with the formula c 3 h 6 propene, there are several alkenes with the formula c 4 h 8. Table below shows some homologous series and their respective general formula and functional group. Methane gas is the first member of the homologous series of alkanes. These properties typically change gradually along the series, and the changes can often be explained by mere differences in molecular size and mass. Alkynes have fewer hydrogens than either alkanes or alkenes, and their general formula is cnh2n2. Organic chemistry alkanes, alkenes, alcohols and carboxylic. Unlike alkanes, alkenes can undergo addition reactions due to the cc double bond, and are therefore called unsaturated hydrocarbons.
The homologous series is a family or group of hydrocarbons or derivatives having the same functional group, same general formula and similar chemical properties. Choose from 352 different sets of homologous series flashcards on quizlet. Alkenes are organic compounds that are generally only comprised of hydrogen and carbon atoms. What are the general formulas for alkane, alkene, alkyne. All compounds in homologous series have functional group except alkanes. They have the general formula cnh2n, as they contain two hydrogen atoms less than the alkanes, alkenes are called unsaturated hydrocarbons. The general formula for the alkenes is c n h 2n, where n is the number of carbon atoms in the molecule. Significance and properties of the homologous series. Give the general formula for the molecular formula of the alkene homologous series. What is the general formula of the homologous series of. Natures chemistry homologous series national 5 chemistry. Using this formula, we can write a molecular formula for any alkane with a given number of carbon atoms.
For example, alkane is a homologous series, alkene is a homologous series, alcohol is also a homologous series. How are alkanes, alkenes, and alkynes homologous series. The 1st member to possess this functional group is ethane, c 2 h 4. This group of compounds comprises a homologous series with a general molecular formula of c n h 2 n, where n equals any integer greater than one. Alkene definition of alkene by the free dictionary. Their general formula, physical and chemical properties. This organic chemistry note for igcse chemistry covers the three major homologous series alkane, alkene, and alcohols. After these the names are formed by adding the ending ane to the greek word for the number of carbon atoms in the molecule. Alkene series definition, the homologous series of unsaturated, aliphatic hydrocarbons containing one double bond and having the general formula cnh2n, as ethylene, h2cch2.
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