Bromoethane (CH3CH2Br) and KOH Reaction and Mechanism
Bromoethane (CH3CH2Br) reacts differently with KOH according to the medium. If alcoholic KOH is used, ethene is given as the product. Otherwise, with aqueous KOH, ethanol is formed. In this tutorial, we will learn those reactions and products.
Bromoethane | CH3CH2Br
Bromoethane (ethyl bromide) is an alkyl halide compound. At room temperature, bromoethane exists as a gas. Bromoethane reacts with potassium hydroxide (KOH) in two ways.
- Bromoethane and alcoholic KOH reaction
- Bromoethane and aqueous KOH reaction
When an alkyl halide compound is heated with an alcoholic alkali, an alkene is formed as the organic product.
Bromoethane and alcoholic KOH reaction
When bromoethane is heated with alcoholic potassium hydroxide, a water molecule is eliminated from the bromoethane molecule and ethene is given as the product.
CH3CH2Br + alc. KOH → CH2=CH2 + KBr + H2O
To occur the reaction, heat should be provided.
When an alkyl halide compound is heated with an aqueous alkali, an alcohol is formed as the organic product.
Bromoethane and aqueous KOH reaction
When bromoethane is treated with aqueous KOH, ethanol (a primary alcohol compound) is given. Bromine atom of bromoethane is removed and a hydroxyl group is attached. during the reaction.
CH3CH2Br + aq. KOH → CH3CH2OH + KBr
Mechanism of bromoethane and aqueous KOH reaction
Alkyl halide and aqueous alkali reaction can be occurred as a single step or two step reactions. This depends on the formed intermediate carbocation stability. A carbocation can be generated during the reaction.
- Because secondary carbocations and tertiary carbocations are stable, those kind of alkyl halides' reactions occurs through a two step process.
- But, primary carbocations are not stable. Therefore, primary alkyl halide and KOH reaction occurs through a single step. Therefore, there is no carbocation generation in bromoethane and aqueous KOH reaction as a intermediate product.
Bromoethane is an primary alkyl halide and it can form a unstable primary carbocation. Therefore, carbocation is not produced by the bromoethane and aqueous KOH reaction. It happens as a single step reaction as below. When hydroxyl ion attacks the carbon atom, bromine atom is eliminated to give ethanol.
Questions asked by students.
What will happen ch3ch2br + koh(aq)
KOH(aq) is aqueous KOH which is used to convert alkyl halide to an alcohol. Therefore, CH3CH2Br will be converted to CH3CH2OH by KOH(aq).
What is alcoholic KOH and and how to produce alcoholic KOH?
When potassium hydroxide (KOH) exists in a alcohol compound such as ethanol, it is said that an alcoholic KOH solution.
What are the differences of mechanisms in alcoholic and aqueous KOH with Bromoethane?
Hydroxyl ions attack beta hydrogen atom when alcoholic KOH is used. A water molecule is formed as a result of it . With that, bromine atom is eliminated to make a double bond (alkene group) between carbon atoms.In the presence of aqueous KOH, hydroxyl ion attacks directly the carbon atom which is connected with bromine atom. With that new C-OH bond is formed and bromine atom is removed.