Alkanes alkenes and alkynes

Alkanes, Alkenes vs Alkynes Alkanes, alkenes and alkynes are all hydrocarbons with different structures and thus different physical and chemical properties. Hydrocarbons In the study of organic chemistry, the organic compounds which are made up of carbon and hydrogen are called hydrocarbons. They can be gases as, propane, they can be liquids, for example, benzene, or they can be low-melting solids and waxes, for example, polystyrene. There are four classifications of hydrocarbons; saturated hydrocarbons or alkanes, unsaturated hydrocarbons or alkenes and alkynes, cycloalkanes, and aromatic hydrocarbons or arenes.

Alkanes alkenes and alkynes

In contrast to the hydrogenation of alkenes, the addition of molecular bromine or chlorine to produce vicinal dihalogenides does not require catalysts. Bromine or chlorine are the best choices for the halogenation of alkenes. Fluorine reacts very vigorously to form not only fluorinated but also several oxidation products.

The addition of iodine to alkenes is thermodynamically unfavorable. The addition of halogens bromine or chlorine to the double bond of alkenes could follow several mechanisms. A mechanism analogous to the hydrogenation of alkenes would add the halogen atoms from the the same side and only yield the cis product.

A two-step mechanism proceeding through an intermediate carbenium ion similar to the addition of hydrogen halides to double bonds would form the cis as well as the trans product. For example, the bromination of cyclopentene would yield cis-1,2-cyclopentane and trans-1,2-cyclopentane.

However, only the trans product is observed, indicating that anti addition occurs selectively. Therefore the actual mechanism of the halogenation is obviously different from that of hydrogenation and HX addition. Addition of bromine to cyclohexene on a laboratory scale. The result is a partially positive and a partially negatively charged bromine atom.

Subsequently, the bromine-bromine bond is cleaved heterolytically and an intermediate cyclic bromonium ion is formed by the addition of the partially positively charged bromine atom to the double bond. The postulated existence of a cyclic bromonium ion explains the stereochemical outcome of the halogenation.

For steric reasons, nucleophilic attack of the bromine anion at the rigid three-membered ring can only occur from the side opposite to the bromine atom in the ring.

The ring opening reaction follows a S N 2 mechanism. In symmetrically-substituted alkenes no preference of attack at a particular ring carbon atom is observed and it is not expected resulting in a racemic compound as the final product. If the reaction is carried out in a nucleophilic solvent, such as H2O or an alcohol, the attacking species in the nucleophilic ring opening of the cyclic intermediate is the solvent molecule rather than the halide ion.

Key Questions

In the halohydrin reaction, the reagents, HOCl or HOBr, are often generated in situ by reaction of water with chlorine or bromine, respectively. Under specific reaction conditions, HOI also adds to double bonds.The nomenclature of substituted benzene ring compounds is less systematic than that of the alkanes, alkenes and alkynes.

Alkanes alkenes and alkynes

A few mono-substituted compounds are named by using a group name as a prefix to "benzene", as shown by the combined names listed below. What is produced by the action of acids with active metals?

Active metals react with acids to produce hydrogen gas and a salt. The general equation of this type . Alkanes with more than three carbon atoms can be arranged in various different ways, forming structural simplest isomer of an alkane is the one in which the carbon atoms are arranged in a single chain with no branches.

When it comes to Alkanes, Alkenes, and Alkynes, the acidity is in the order of Alkynes > Alkenes > Alkanes. The acidity is mainly due to the increase in the s-character which causes an increase in acidity. Unsaturated hydrocarbons are hydrocarbons that have double or triple covalent bonds between adjacent carbon with at least one carbon-to-carbon double bond are called alkenes and those with at least one carbon-to-carbon triple bond are called alkynes.

The position of the double or triple bond is shown by a number written either at the start of the name, or just before the -ene or.

Photo synthesis Using light to produce Solar energy is converted into chemical energy. Photosynthesis is the process whereby plants using light energy from the sun convert carbon dioxide and water to glucose sugar and oxygen gas through a series of reactions. The overall equation for photosynthesis is. carbon dioxide + water =light energy=> glucose + oxygen. Alkenes and alkynes can be transformed into almost any other functional group you can name! We will review their nomenclature, and also learn about the vast possibility of reactions using alkenes and alkynes as starting materials. What is produced by the action of acids with active metals? Active metals react with acids to produce hydrogen gas and a salt. The general equation of this type .

Absorptions in Alkenes C-H stretch occurs in region of – cm-1 (note higher wavenumber relative to alkanes) C=C stretch occurs in region of – .

Reactions of Alkenes (Halogenation) - Chemgapedia