In biology, homology is similarity due to shared ancestry between a pair of structures or genes in different taxa. In the field of organic chemistry, a homologous series is a series of compounds with the same functional group and similar chemical properties in which the members of the series can be branched or unbranched. All the members of a homologous series can be represented by a general formula. The alkane series is an organic homologous series consisting of repeating ch2 units. Homologous series is a series of compounds with similar chemical properties and same functional group differing from the successive member. There are some inorganic molecules that can have homologous series too.
As for other types of organic compounds, there are also some nonstandard names for esters. This is a homologous structure to the ovipositor of other organisms like insects and certain fish. A homologous series is a series of organic compounds which belong to the same family i. Another approach to the problem is to consider what happens to the properties of a related series of compounds of increasing chain length.
Structural isomers definition, types and examples chemistry. Each member of a homologous series is called a homologue, which can also be spelled homolog. For example, methane, ethane, propane, butane, etc. Introduction to organic chemistry chemistry alevel revision. Two types of properties of substances of all types, incl. A series of compounds in which successive members differ from one another by a ch 2 unit is called a homologous series. A homologation reaction is a chemical process that converts one member of a homologous series to the next member. Cells containing multiples of the normal chromosome number are called polyploid, those with irregular numbers aneuploid. Examples of functional groups, homologous series, general formula, displayed formula, graphic formula, molecular formula, skeletal formula, structural formula, empirical formula of molecules etc. In organic chemistry, the term homologous series refers to where compounds can differ by the length of their carbon chain. In chemistry, a homologous series is a series of compounds with the same general formula, usually varying by a single parametersuch as the length of a carbon chain. What is homologous series explain with an example science.
In a homologous series there is a gradual increase in boiling point as the number of carbon atoms increases. A homologous series is a group of chemicals which have similar chemical properties and can be represented by a general formula. The ch 2 group is nonpolar hydrophobic and this increases the percentage of the molecule that is unattractive to water. Such series are most common among organic compounds, the structural difference being a methylene group, as in the paraffin hydrocarbons, or. A homologous series in organic chemistry is a group of organic compounds compounds that contain carbon c atoms that diverge from each other by one methylene ch 2 group. The modified leaves of carnivorous plants, cacti and poinsettias is another example, as is the skeletal structures of whales and hummingbirds. Use homologous in a sentence homologous sentence examples. The successive members vary from each other by a ch 2 unit.
The alkanes, alkenes and cycloalkanes are examples of homologous series. Organic functional groups homologous series explained why. The individual members of a homologous series are called homologues and the phenomenon is called homology. A homologous series is a series of carbon compounds that have different numbers of carbon atoms but contain the same functional group. Homologous series are referenced frequently in organic chemistry, where compounds can differ by the length of their carbon chain. A homologous series is a group of chemicals which have similar chemical. Where, n is the number of carbon atoms in alkyne molecule. Following are the characteristics of a homologous series. These structures do not have to look exactly the same, or have the same function.
These atoms or groups attached are known as functional groups and the series formed are all homologous series. Open and closed chain hydrocarbons let us observe the. Examples concern all levels of organization such as molecules of a specific protein, homologous chromosomes or mitochondria in a cell or an organism, hairs of a mammal, legs or segments of an arthropod, any structure represented symmetrically in an organism, etc. Examples of homologous structures that reveal our shared. 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. All the members of homologous series of alkynes have similar structure and similar chemical properties, so they can be grouped together into the homologous series. 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. All the compounds of a homologous series show similar chemical properties. Cbse class 10 science carbon and its compounds the family of organic compounds have same functional group, similar chemical properties and their successive member differ by a. The concept of homologous series was proposed in 1843 by the french chemist charles gerhardt. Homologous series have the same general formula with the neighbouring members of the series differing by ch 2. This section of revision science is an introduction to organic chemistry.
T he numerous organic compounds can be grouped into a comparatively small number of series or families of compounds known as homologous series. More than 98 percent of natural crude rubber is a hydrocarbon polymer, a chainlike molecule consisting of many units linked together. The standard system for naming esters uses the suffix oate to indicate that a molecule is an ester. For example, lets look at some of the possible structures and. In first year organic chemistry, the first ten names of the homologous series are usually all that need to be memorized. For example, methane, ethane, and propane are part of a homologous series. For example, the first alkane is methane, which has a formula of ch4. Now that you have seen these examples of homologous structures, you can observe many different examples in nature. A common example of homologous structures is the forelimbs of vertebrates, where the wings of bats and birds, the arms of primates, the front flippers of whales and the forelegs of fourlegged vertebrates like dogs and crocodiles are all derived from the same ancestral tetrapod.
The difference between each member of an homologous series is one ch 2 unit. A series of compounds with similar chemical properties, in which members differ from one another by the possession of an additional ch2 group, is called a homologous series. Types of chromosomal aberrations in man are of two general types. For the term series, the series diverges if the limit of the sequence of it terms is not zero this is really not a test for convergence and must be used with care. Homologous series arent just limited to organic compounds. In organic chemistry, a homologous series is a series of compounds with the same general formula, usually varying by a single parameter. In chemistry, a homologous series is a group of compounds that share the same. Homologous structures were such as, though greatly differing in appearance and detail from one another, and though performing widely different functions, yet were capable of being shown by adequate study of a series of intermediate forms to be derived from one and the same part or organ of the planform or archetype. The most common series include alkanes, ethers, and alcohols.
Oct 12, 2015 in organic chemistry, the term homologous series refers to where compounds can differ by the length of their carbon chain. Some of the alternative names used for the simple esters shown in the tables of examples on this page are listed in the column under the heading synonyms. Homologous series of alkanes, alkenes and alkynes with. Dec 12, 2016 types of chromosomal aberrations in man are of two general types. The types of homology and their significance for evolutionary. Here we define the term homologous series and give some examples of series. In this variety of structural isomerism, the isomers contain different functional groups that is, they belong to different families of compounds different homologous series. Many different types of compounds have homologous series. In chemistry, a homologous series is a series of compounds with the same general formula, usually varying by a single parametersuch as the. Why many different homologous series of organic compounds. The structures and chemistry of individual hydrocarbons depend in large part on the types of chemical bonds that link together the atoms of their constituent molecules. Hydrocarbons are molecules that are made up of hydrogen and carbon atoms. There are two types of homologous genes, each defined by.
For example, a molecular formula c 3 h 6 o could be either propanal an aldehyde or propanone a ketone. The simplest precedent is the sequence of properties for the saturated paraffin hydrocarbons normal alkanes. If two series are such that for all values of n where 0 less than or. Introduction to homologous series and functional groups. These differences can have an effect on the physical properties of the chemicals, such as boiling point. Such a series of compounds is known as an homologous series.
The members of this series are called homologue and differ from each other by the number of ch 2 units in the main carbon chain. The homologous series of straightchained alkanes begins methane ch 4, ethane c 2 h 6, propane c 3 h 8, butane c 4 h. Organic compounds consequently tend to be less soluble as an homologous series is ascended. Homologous series, any of numerous groups of chemical compounds in each of which the difference between successive members is a simple structural unit. 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. Homologous structures examples range from the finger bones of human hands and bat wings to the legs of mice, crocodiles and other fourlegged vertebrates. The main difference between compounds in such series is the addition of an extra carbon and dihydrogen group, ch2. Notes on functional group and homologous series grade 11. Carbon and its compounds homologous series youtube. Best types of chromosomal aberrations with great examples. Some of the examples of homologous series are as follows. Open chain hydrocarbons are also called aliphatic hydrocarbons or acyclic hydrocarbons. Homologous structures were such as, though greatly differing in appearance and detail from one another, and though performing widely different functions, yet were capable of being shown by adequate study of a series of intermediate forms to be derived from one and the same part or.
Homologous series definition in the cambridge english. Nov 14, 2016 homologous structures are organs or skeletal elements of animals and organisms that, by virtue of their similarity, suggest their connection to a common ancestor. This can be the length of a carbon chain, for example in the straightchained. Monosaccharides and disaccharides comprise the smallest types of carbohydrates. It is important that you commit to memory the names of the first 10 straightchain alkanes i. Significance and properties of the homologous series gulpmatrix. For example, methane and ethane are homologues and. Predict and explain the trends in boiling points of members of a homologous series.
Why many different homologous series of organic compounds and. Examples of homologous structures pair of chromosomes possessing alleles of the same genes, and having the same overall shape, size, and structure are called homologous chromosomes. Within a given homologous series the chemical properties of the compounds are essentially all alike, and the physical properties vary in a continuous and predictable manner. Hydrocarbons are classified into two categories known as open chain hydrocarbons and closed chain hydrocarbons. Homologous structures definition and examples biology. We shall study this series to illustrate what a homologous series means. Nov 14, 2017 metamerism is a type of structural isomerism where the isomers have same molecular formula but differ due to the different number of carbon atoms or alkyl groups on either side of functional group i. Homologous series of alkanes, alkenes and alkynes with examples. The potato tuber, ginger rhizome, and the fleshy part of cacti are homologs as they are all modified stems. Homologous series of inorganic compounds include the phosphoric acids, the silicic acids, and the phosphonitrilic chlorides. Homologous genes are, therefore, different than analogous genes, which evolve independently in different species to fill a similar purpose. Homologous series are referenced frequently in organic chemistry, where compounds can. The general formula of homologous series of alkynes is c n h 2n2. Saturated hydrocarbons alkanes are the simplest of the hydrocarbon species.
If two series are such that for all values of n where 0 less than or equal to which is also equal to or less than. Homologous series meaning in the cambridge english. For example, the general formula of the homologous series of. The second alkane is ethane, which has two carbon atoms. Biopolymers also form homologous series, for example the polymers of glucose such as cellulose oligomers starting with cellobiose, or the series of amylose oligomers starting with maltose, which are sometimes called maltooligomers. The only difference among these molecules is that they have different numbers of ch 2 groups. The individual members of a homologous series are known as homologous and the process is known as homology. Types of food additives and their functions a plus topper. Some examples of homologous series are shown in the following table. Each homologous series must have the following four characteristics. Identify the homologous series to which the compound shown below belongs. The simplest series of compounds in organic chemistry is the alkanes.
Natures chemistry homologous series national 5 chemistry. The number of carbons continuously bonded together is an important structural feature and is described using the homologous series. Each alkane has two hydrogen atoms in addition to its ch2 units. Saturated means that all of these atoms are held together by single covalent bonds. Classification of hydrocarbons the compounds containing only carbon and hydrogen in their molecules are called hydrocarbons. Homologous series meaning in the cambridge english dictionary. Homologous series examples, answers, activities, experiment. Homologous series wikimili, the best wikipedia reader.
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