Question
Read the passage given below and answer the following questions from 1 to 5.
The three-dimensional (3-D) structure of organic molecules can be represented on paper by using certain conventions. For example, by using solid ( ) and dashed ( ) wedge formula, the 3-D image of a molecule from a two-dimensional picture can be perceived. In these formulas the solid-wedge is used to indicate a bond projecting out of the plane of paper, towards the observer. The dashed-wedge is used to depict the bond projecting out of the plane of the paper and away from the observer. Wedges are shown in such a way that the broad end of the wedge is towards the observer. The bonds lying in plane of the paper are depicted by using a normal line (—). 3-D representation of methane molecule on paper has been shown in Figure.
A cyclic or open chain componds these compounds are also called as aliphatic componds and consist of staright or branched chain componds for example:
Cyclic or closed chain or ring compounds
a) Alicyclic compounds Alicyclic (aliphatic cyclic) compounds contain carbon atoms joined in the form of a ring (homocyclic).
Someetimes atoms other than carbon are also present in the ring (heterocylic). Tetrahydrofuran given below is an example of this types of compound:
These exhibit some of the properties similar to those of aliphatic compounds.
b) Aromatic compounds Aromatic compounds are special types of compounds. These include benzene and other related ring compounds (benzenoid). Like alicyclic compounds, aromatic comounds may also have hetero atom in the ring. Such compounds are called hetrocyclic aromatic compounds. Some of the examples of various types of aromatic compounds are:
Benzenoid aromatic compounds .
Organic compounds can also be classified on the basis of functional groups, into families or homologous series.
Functional Group The functional group is an atom or a group of atoms joined to the carbon chain which is responsible for the characteristic chemical properties of the organic compounds. The examples are hydroxyl group (–OH), aldehyde group (–CHO) and carboxylic acid group (–COOH) etc.
Homologous Series A group or a series of organic compounds each containing a characteristic functional group forms a homologous series and the members of the series are called homologues. The members of a homologous series can be represented by general molecular formula and the successive members differ from each other in molecular formula by a $–CH^2$ unit. There are a number of homologous series of organic compounds. Some of these are alkanes, alkenes, alkynes, haloalkanes, alkanols, alkanals, alkanones, alkanoic acids, amines etc. It is also possible that a compound contains two or more identical or different functional groups. This gives rise to polyfunctional compounds.
A systematic name of an organic compound is generally derived by identifying the parent hydrocarbon and the functional group(s) attached to it. See the example given below.
By further using prefixes and suffixes, the parent name can be modified to obtain the actual name. Compounds containing carbon and hydrogen only are called hydrocarbons. A hydrocarbon is termed saturated if it contains only carbon-carbon single bonds.
The IUPAC name for a homologous series of such compounds is alkane. Paraffin (Latin: little affinity) was the earlier name given to these compounds. Unsaturated hydrocarbons are those, which contain at least one carbon- carbon double or triple bond. IUPAC Nomenclature of Alkanes Straight chain hydrocarbons: The names of such compounds are based on their chain structure, and end with suffix ‘-ane’ and carry a prefix indicating the number of carbon atoms present in the chain (except from $CH_4$ to $C_4H_{10}$, where the prefixes are derived from trivial names). The IUPAC names of some straight chain saturated hydrocarbons are given in Table. The alkanes in table differ from each other by merely the number of $– CH_2$ groups in the chain. They are homologues of alkane series.
The three-dimensional (3-D) structure of organic molecules can be represented on paper by using certain conventions. For example, by using solid ( ) and dashed ( ) wedge formula, the 3-D image of a molecule from a two-dimensional picture can be perceived. In these formulas the solid-wedge is used to indicate a bond projecting out of the plane of paper, towards the observer. The dashed-wedge is used to depict the bond projecting out of the plane of the paper and away from the observer. Wedges are shown in such a way that the broad end of the wedge is towards the observer. The bonds lying in plane of the paper are depicted by using a normal line (—). 3-D representation of methane molecule on paper has been shown in Figure.
A cyclic or open chain componds these compounds are also called as aliphatic componds and consist of staright or branched chain componds for example:
Cyclic or closed chain or ring compounds
a) Alicyclic compounds Alicyclic (aliphatic cyclic) compounds contain carbon atoms joined in the form of a ring (homocyclic).
Someetimes atoms other than carbon are also present in the ring (heterocylic). Tetrahydrofuran given below is an example of this types of compound:
These exhibit some of the properties similar to those of aliphatic compounds.
b) Aromatic compounds Aromatic compounds are special types of compounds. These include benzene and other related ring compounds (benzenoid). Like alicyclic compounds, aromatic comounds may also have hetero atom in the ring. Such compounds are called hetrocyclic aromatic compounds. Some of the examples of various types of aromatic compounds are:
Benzenoid aromatic compounds .
Organic compounds can also be classified on the basis of functional groups, into families or homologous series.
Functional Group The functional group is an atom or a group of atoms joined to the carbon chain which is responsible for the characteristic chemical properties of the organic compounds. The examples are hydroxyl group (–OH), aldehyde group (–CHO) and carboxylic acid group (–COOH) etc.
Homologous Series A group or a series of organic compounds each containing a characteristic functional group forms a homologous series and the members of the series are called homologues. The members of a homologous series can be represented by general molecular formula and the successive members differ from each other in molecular formula by a $–CH^2$ unit. There are a number of homologous series of organic compounds. Some of these are alkanes, alkenes, alkynes, haloalkanes, alkanols, alkanals, alkanones, alkanoic acids, amines etc. It is also possible that a compound contains two or more identical or different functional groups. This gives rise to polyfunctional compounds.
A systematic name of an organic compound is generally derived by identifying the parent hydrocarbon and the functional group(s) attached to it. See the example given below.
By further using prefixes and suffixes, the parent name can be modified to obtain the actual name. Compounds containing carbon and hydrogen only are called hydrocarbons. A hydrocarbon is termed saturated if it contains only carbon-carbon single bonds.
The IUPAC name for a homologous series of such compounds is alkane. Paraffin (Latin: little affinity) was the earlier name given to these compounds. Unsaturated hydrocarbons are those, which contain at least one carbon- carbon double or triple bond. IUPAC Nomenclature of Alkanes Straight chain hydrocarbons: The names of such compounds are based on their chain structure, and end with suffix ‘-ane’ and carry a prefix indicating the number of carbon atoms present in the chain (except from $CH_4$ to $C_4H_{10}$, where the prefixes are derived from trivial names). The IUPAC names of some straight chain saturated hydrocarbons are given in Table. The alkanes in table differ from each other by merely the number of $– CH_2$ groups in the chain. They are homologues of alkane series.
| Name | Molecular formula | Name | Molecular Formula |
| Methane | $CH_4$ | Heptane | $C_7H_{16}$ |
| Ethane | $C_2H_6$ | Octane | $C_8H_{18}$ |
| Propane | $C_3H_8$ | Nonane | $C_9H_{20}$ |
| Butane | $C_4H_{10}$ | Decane | $C_{10}H_{22}$ |
| Pentane | $C_5H_{12}$ | Icosane | $C_{20}H_{42}$ |
| Hexane | $C_6H_{14}$ | Triacontane | $C_{30}H_{62}$ |
- IUPAC is an acronym for …
- International Union of Pure and Applied Chemistry
- International units of proteins and carbohydrates
- International understandings on physical aspects of chemistry
- Iodine under packings
- In homologous series, the successive members differ from each other in molecular formula by a … unit.
- $CH_3$
- $CH_2$
- $CH$
- $CH_4$
- A hydrocarbon is termed saturated if it contains only carbon-carbon … bonds.
- Triple
- Double
- Single
- Zero
- From ….., where the prefixes are derived from… trivial names.
- $CH_4$ to $C_2H_6$
- $CH_4$ to $C_3H_8$
- $CH_4$ to $C_6H_{14}$
- $CH_4$ to $C_4H_{10}$
- Molecular formula of octane is …
- $C_4H_{10}$
- $C_6H_{14}$
- $C_2H_6$
- $C_8H_{18}$
