BENZENE VS ALKENES

Introduction

Benzene and alkenes are both types of organic compounds that contain unsaturated carbon-carbon bonds. However, there are some significant differences in their chemical properties and reactions.

1. Reactivity: Alkenes are much more reactive than benzene. This is because the double bond in alkenes is relatively weak, making it easier to break and form new bonds. Benzene, on the other hand, has a stable ring structure that is resistant to many types of chemical reactions.
2. Addition reactions: Alkenes readily undergo addition reactions, where atoms or groups of atoms are added to the double bond. For example, hydrogen gas can be added to an alkene to form an alkane. Benzene, however, is much less reactive and does not undergo simple addition reactions.
3. Aromaticity: Benzene is an aromatic compound, meaning it has a ring structure with alternating double bonds. This structure gives benzene unique chemical properties and stability. Alkenes, on the other hand, do not have this aromaticity and are generally less stable.
4. Substitution reactions: Benzene is highly reactive towards electrophiles, which can substitute one or more of its hydrogen atoms with other functional groups. This substitution reaction is a hallmark of aromatic chemistry and is not typically seen with alkenes.

In summary, while both benzene and alkenes contain unsaturated carbon-carbon bonds, their reactivity and chemical properties are quite different. Alkenes are more reactive and undergo addition reactions readily, while benzene is highly resistant to simple addition reactions but readily undergoes substitution reactions.

 

Differences between the reactivity of benzene and alkenes

Benzene and alkenes differ in their reactivity towards certain reagents due to the unique electronic structure of benzene. Benzene is a highly stable compound due to its aromaticity, which means that its electrons are delocalized over the entire ring structure. This makes it resistant to addition reactions that are typical of alkenes.

Here are some examples of reagents and their reactions with benzene and alkenes:

1) Hydrogenation with H2 and a metal catalyst: Alkenes readily undergo hydrogenation to form saturated hydrocarbons, while benzene is unreactive towards hydrogenation due to its stability:

Alkene: H2 + C2H4 → C2H6

Benzene: no reaction

 

2) Halogenation with Br2 or Cl2: Alkenes readily undergo halogenation to form a vicinal dihalide, while benzene reacts under more extreme conditions, such as the use of a Lewis acid catalyst, to form a polychlorinated or polybrominated benzene:

Alkene: Br2 + C2H4 → BrCH2CH2Br

Benzene: Br2 + FeBr3 → bromobenzene + HBr

 

3) Addition of a strong acid: Alkenes undergo addition of strong acids such as HBr or HCl, while benzene does not react with these acids:

Alkene: HBr + C2H4 → CH3CH2Br

Benzene: no reaction

 

4) Oxidation with KMnO4: Alkenes can be oxidized by KMnO4 to form diols or other oxygenated functional groups, while benzene is resistant to oxidation due to its stability:

Alkene: KMnO4 + C2H4 → HOCH2CH2OH

Benzene: no reaction

In summary, benzene is more stable and resistant to addition reactions compared to alkenes due to its delocalized pi-electron system. This property makes benzene useful as a starting material for many organic synthesis reactions, where selectivity is important.

 

Hexachlorocyclohexane (HCH), also known as benzene hexachloride, is a chemical compound that exists in several forms. One of the forms, known as alpha-hexachlorocyclohexane (α-HCH), was once widely used as an insecticide.

The most common isomer is gamma-hexachlorocyclohexane (γ-HCH)

Here are some of the uses of hexachlorocyclohexane:

1. Insecticide: α-HCH was used as an insecticide to control pests like flies, mosquitoes, and termites. It was also used to control agricultural pests like boll weevils and rice weevils. However, its use as an insecticide has declined significantly due to its persistence in the environment and its potential harmful effects on human health.
2. Industrial uses: HCH has been used in the past as a solvent for fats, oils, waxes, and resins. It was also used in the manufacture of dyes and pharmaceuticals.
3. Medical uses: HCH has been used as a topical treatment for scabies and lice infestations in humans. However, its use as a medical treatment has been largely discontinued due to the availability of safer and more effective alternatives.
4. Veterinary uses: HCH was used to control fleas and ticks in pets and livestock. However, its use in veterinary medicine has declined due to its potential harmful effects on animals and humans.

It is worth noting that the use of HCH as an insecticide and in other applications has been largely discontinued due to its persistence in the environment and potential harmful effects on human and animal health.

 

Uses of (BHC)

Benzene hexachloride (BHC) is an organochlorine compound that has been used for a variety of purposes, including as an insecticide, fungicide, and acaricide. Here are some of its uses:

1. Insecticide: BHC is primarily used as an insecticide, especially for controlling pests that attack crops. It is effective against a wide range of insects, including mosquitoes, flies, and beetles. BHC is applied as a spray or dust on crops, in storage areas, and around homes.
2. Fungicide: BHC is also used as a fungicide to control plant diseases caused by fungi. It is applied as a spray on crops and has been used for controlling powdery mildew on roses, grapes, and other fruits.
3. Acaricide: BHC is used as an acaricide to control mites and ticks that attack crops, livestock, and humans. It is applied as a spray or dust on crops and animals.
4. Veterinary medicine: BHC was also used as a veterinary medicine to control external parasites such as fleas and ticks in domestic animals. However, its use in veterinary medicine has also been largely discontinued due to its potential health risks.
5. Wood preservation: BHC has been used as a wood preservative to protect wood from decay and insect damage. It is applied as a spray or by dipping the wood in a solution of BHC.
6. Research: BHC has been used as a research tool in various studies related to environmental contamination, toxicity, and bioaccumulation.

However, due to its toxicity and persistence in the environment, the use of BHC has been banned in many countries.