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The study of naming the carbon compounds following the IUPAC guidelines is called the nomenclature of hydrocarbons. Except for a few inorganic carbon molecules, all carbon compounds are organic. Inorganic carbon compounds include carbon oxides, metal ion bicarbonates and carbonates, and metal cyanides. Simple hydrocarbon chains with no functional groups are alkanes, alkenes, and alkynes. Alkanes are the most basic organic substances.
Saturated hydrocarbons are alkanes with single bonds between carbon atoms. Alkenes contain one carbon-carbon double bond. One or more carbon-carbon triple bonds characterise alkynes. Unsaturated hydrocarbons include alkenes and alkynes.
The formula for alkanes is CnH2n+2, where n is the number of carbon atoms.
The formula for alkenes is CnH2n.
CnH2n-2 is the general formula for alkynes.
The simplest alkyne is acetylene, which has the formula C2H2. Let us study in detail.
Nomenclature of Hydrocarbons
The following rules are applied in the nomenclature of hydrocarbon Alkanes.
The longest continuous carbon chain must be identified and given a name.
Identify and list the many groups that are linked to this chain.
Start by numbering the chain from the end that is closest to a substituent group.
Assign an appropriate number and name to each substituent group’s location.
Put the name together by listing the groups in alphabetical order.
When alphabetizing, the prefixes di, tri, tetra, and others, used to denote many groups of the same kind, are ignored.
Alkanes
Alkanes are represented by the chemical formulae (CnH2n+2). Each subsequent member of the series contains one more carbon atom than before it. Methane (CH4) is the most basic hydrocarbon. This is the most basic hydrocarbon in the family of hydrocarbons. The alkanes with fewer carbons are lighter and are gases. Alkanes containing carbons 7 to 12 are liquids used in petrol or gasoline. The higher alkanes are waxy solids. Alkanes are saturated, meaning they have the most hydrogens per carbon and have no double or triple bonds.
IUPAC Alkane Nomenclature Rules
Organic nomenclature is the process of naming organic substances. The International Union of Pure and Applied Chemistry has established several standards for naming organic molecules.
Properties of Alkanes
Alkanes have low reactivity.
They are nonpolar solvents.
Water is immiscible with alkanes, although widely miscible in other nonpolar solvents. Because alkanes with weak dipole bonds cannot break the strong hydrogen connection between water molecules, they are not miscible in water.
When alkanes are burned at the same temperature as other hydrocarbons, more significant concentrations of organic molecules containing oxygen, such as aldehydes and ketones, are produced.
Alkenes
The alkenes are a different group of chemicals. CnH2n is the general formula for these. There are fewer hydrogen atoms in alkenes than in alkanes. The valencies that are left behind due to fewer hydrogen bonds form double bonds between two carbon atoms. Alkenes are chemically more reactive because double bonds are more reactive than single ones.
IUPAC Alkene Nomenclature Rules
1. An alkene or cycloalkene is indicated by the ending suffix (ending).
2. Both carbon atoms of the double bond must be included in the root name’s longest chain.
3. The numbering of the root chain must begin at the end closest to a double bond carbon atom. The nearest substituent rule determines the end of the chain where numbering begins if the double bond is in the middle.
4. The double bond locator is the smallest of the two numbers denoting the carbon atoms of the double bond. If there is more than one double bond, the compound is given a diene, triene, or comparable prefix to indicate the number of double bonds, and each double bond is given its name.
5. The double bond carbons in cycloalkanes are assigned to ring positions 1 and 2. The closest substituent rule can determine which of the two is 1.
6. Substituent groups with double bonds include:
Vinyl group H2C=CH
Allyl group H2C=CH–CH2–
Properties of Alkenes
Due to the relative instability of the pi bond, alkenes are more reactive than their related alkanes.
The regularity with which alkenes can pack and the contact surface area determine their melting and boiling points.
Alkenes have rotation restrictions around the double bond, resulting in diastereoisomers with distinct substitution sequences.
Alkynes
The alkynes are the third group. CnH2n-2 is the chemical formula for these. A triple bond connects two carbon atoms in an alkyne. As a result of the high reactivity, these molecules are unstable. They are nonpolar, unsaturated hydrocarbons with physical properties analogous to alkanes and alkenes. Alkynes are soluble in organic solvents, slightly soluble in polar solvents, and insoluble in water. Alkynes have slightly higher boiling points than alkanes and alkenes.
Ethane, for example, has a boiling point of -88.6°C, but ethene has a boiling point of -103.7°C, and ethyne has a boiling temperature of -84.0°C.
Nomenclature of Alkynes
Nomenclature of hydrocarbon Alkynes follows these rules:
Alkynes have the empirical formula CnH2n-2 and are organic compounds with the functional group carbon-carbon triple bonds. They are unsaturated hydrocarbons. Alkynes have the suffix –yne, which is used because there is just one alkyne in the molecule, similar to how alkenes have the suffix –ene.
When a molecule has both a double and a triple bond, the carbon chain is numbered with the first multiple bonds at the bottom. The double bond takes precedence if both bonds may be assigned the same number. Subsequently, the molecule is given the name “n-en-n-yne,” with the double bond root name coming first (e.g. 2-hepten-4-yne).
Conclusion
Hydrocarbons are the simplest organic compounds and are made up of only carbon and hydrogen atoms. Thus compounds of only carbon and hydrogen are called hydrocarbons, and the nomenclature of hydrocarbons follow fixed guidelines. Simple hydrocarbon chains with no functional groups are alkanes, alkenes, and alkynes. Alkanes are the most basic organic substances.
