Differentiation between cyclohexene and benzene and ethylbenzene

In organic chemistry, cyclohexene, benzene and ethylbenzene are three substances that are often confused, and they have significant differences in structure and properties. This article will analyze how to distinguish these three substances in detail from the aspects of structure, physical properties, chemical reactions and identification methods.

STRUCTURE AND PROPERTIES OF CYCLOHEXENE

Cyclohexene is a cyclic compound whose structure consists of a six-carbon ring structure with a double bond in the ring. Specifically, the structural formula of cyclohexene is: C6H10. Due to the presence of double bonds, cyclohexene has a certain degree of unsaturation and is prone to addition reactions.

Chemical properties: Cyclohexene will react with bromine water under light conditions to generate 1,2-dibromohexane. The conditions for this reaction are usually light or ultraviolet light, and the reaction phenomenon is characterized by the fading of bromine water and the formation of white precipitate.

Physical properties: Cyclohexene has the appearance of oily or waxy, is slightly more dense than water, has a melting point of about 61°C and a boiling point of about 142°C. It is stable at room temperature, but it is easy to decompose under light.

BENZENE STRUCTURE AND PROPERTIES

Benzene is a typical aromatic hydrocarbon with a structural formula of C6H6. It consists of six carbon atoms arranged in a planar regular hexagonal structure, with one hydrogen atom attached to each carbon atom. Benzene is extremely aromatic, with a Density of 0. Unlike many organic compounds, benzene is liquid under standard conditions and has a density of about 0.89g/cm³.

Chemical properties: Benzene does not have an addition reaction with bromine water, but a substitution reaction occurs. Under the condition of light, benzene and bromine water will be replaced by a reaction, resulting in a white precipitate, the reaction formula is C6H6 Br2 → C6H5Br HBr.

Physical properties: Benzene is liquid at room temperature and has a characteristic oily appearance with a melting point of 5.5°C and a boiling point of 80.1°C. It is insoluble in water, but soluble in organic solvents.

THE STRUCTURE AND PROPERTIES OF ETHYLBENZENE

Ethylbenzene is an organic compound whose structural formula is C6H5-CH2CH3. It consists of a phenyl ring linked to an ethyl group (CH2CH3). Compared with benzene, ethylbenzene has an additional alkyl group in its structure, which makes its chemical properties different from benzene.

Chemical properties: Ethylbenzene will also react with bromine water under light conditions to generate a white precipitate. However, the reaction rate is slower compared to benzene. This is because an alkyl group is added to the ethylbenzene molecule, and the alkyl group partially hinders the structure of the benzene ring and reduces the substitution position of the bromine atom.

Physical properties: Ethylbenzene is liquid under standard conditions and has a density of approximately 0.876g/cm³. It has a melting point of about 5.1°C and a boiling point of about 135.7°C. Ethylbenzene is insoluble in water, but is soluble in organic solvents.

How to identify cyclohexene, benzene and ethylbenzene

1. bromine water reaction phenomenon

• Cyclohexene: in the light conditions and bromine water addition reaction, bromine water fade.
• Benzene: not with bromine water addition reaction, but with bromine water substitution reaction, the formation of white precipitate.
• Ethylbenzene: in the light conditions and bromine water substitution reaction, the formation of white precipitate, but the reaction rate is slow.

1. Solubility:

• Cyclohexene: oily or waxy appears, slightly more dense than water.
• Benzene: in standard conditions for liquid, density of about 0.89 g/cm ³.
• Ethylbenzene: Under standard conditions, it is liquid and has a density of about 0.876g/cm³.

1. Reactivity:

• Benzene substitution reaction rate is slow, and ethylbenzene substitution reaction rate is faster.
• Cyclohexene addition reaction easily proceeds, while benzene and ethylbenzene addition reaction does not easily occur.

Through the above identification methods, cyclohexene, benzene and ethylbenzene can be accurately distinguished. These three substances have significant differences in structure and properties. It is very important to master their identification methods for the study and practical application of organic chemistry.