Why are alkenes are unsaturated?
Alkenes are called unsaturated molecules because two atoms can join onto half of the carbon = carbon double bond when it opens up. In other words they potentially have spare bonds to link up with other atoms and alkanes cannot do this.
In organic chemistry, an alkene is an unsaturated hydrocarbon that contains at least one carbon–carbon double bond. The words alkene and olefin are often used interchangeably (see nomenclature section below).
- Dienes are alkenes with 2 double bonds. IUPAC: Same as alkene, but change -ene to -adiene and use two numbers to locate the two double bonds (number from the end of the chain which makes the smaller of these numbers smaller). Double bonds separated by more than one single bond are isolated.
- Alkynes: Molecular and Structural Formulas. The alkynes comprise a series of carbon- and hydrogen-based compounds that contain at least one triple bond. 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.
- The alkanes are highly combustible and are valuable as clean fuels, burning to form water and carbon dioxide. Methane, ethane, propane and butane are gases and used directly as fuels. Alkanes from pentane up to around C17H36 are liquids. Gasoline is a mixture of alkanes from pentane up to about decane.
Alkenes are unsaturated hydrocarbons. They contain a double bond, which is shown as two lines between two of the carbon atoms. The presence of this double bond allows alkenes to react in ways that alkanes cannot. They can react with oxygen in the air, so they could be used as fuels.
- NO Benzene is an aromatic compound. It doesn't contain any double bonds therefore it cannot be an alkene. The bond in benzene is delocalised, i.e. the electrons are spread over more than one bond. The actual bond enthalpy is an intermediate between a single bond and a double bond.
- Paraffins is a Latin word meaning (parum = little + affinis = reactivity).Alkanes are called paraffins because they have a little affinity towards a general reagent. In other words,alkanes are inert substances. They undergo reactions under drastic conditions.
- There are two other types of basic hydrocarbons: alkenes and alkynes. Alkenes contain less hydrogen, carbon for carbon, than the alkanes. To account for this difference, the carbon atoms are joined by a double bond. The carbon-carbon double bond is the distinguishing feature of the alkene structure.
Updated: 25th September 2018