Question

Describe what is meant by each of the following reaction types, and illustrate with an example from the text: (a) dehydration; (b) hydrolysis; (c) solvolysis; (d) hydration of an alkene.

Short answer

(a) Dehydration: A reaction where a molecule of water is removed from a substance. Example: Ethanol to ethene and water. (b) Hydrolysis: A reaction involving the breaking of a bond in a molecule using water. Example: Ethyl ethanoate to ethanol and ethanoic acid. (c) Solvolysis: A reaction where a solute is broken down, in part, by a solvent. Example: Tertiary butyl chloride to tertiary butyl alcohol. (d) Hydration of an alkene: A reaction where water is added to an alkene to produce an alcohol. Example: Ethene to ethanol.

Step-by-step solution

Identify and Explain Dehydration

Dehydration is a type of chemical reaction where a molecule of water is removed from a substance. For instance, Ethanol (\(C_2H_{5}OH\)) can undergo a dehydration reaction to produce ethene (\(C_2H_{4}\)) and water (\(H_2O\)).

Identify and Explain Hydrolysis

Hydrolysis is a reaction involving the breaking of a bond in a molecule using water. A good example is the hydrolysis of ester- Ethyl ethanoate (\(CH_{3}COOC_{2}H_{5}\)). In this reaction, the ester reacts with water to form ethanol and ethanoic acid.

Identify and Explain Solvolysis

Solvolysis is a type of reaction where a solute is broken down, in part, by a solvent. For instance, tertiary butyl chloride (\( (CH_{3})_{3}CCl \)) can undergo solvolysis when treated with water to give tertiary butyl alcohol (\( (CH_{3})_{3}COH \)).

Identify and explain Hydration of an Alkene

Hydration of an alkene is a reaction where water is added to an alkene to produce an alcohol. For example, the hydration of ethene (\(C_{2}H_{4}\)) yields ethanol (\(C_{2}H_{5}OH\)).

Key concepts

Dehydration Reactions

In chemistry, dehydration reactions are processes where a molecule loses water. This often involves removing an

• hydroxyl group (−OH), and
• a hydrogen atom (H)

rather than breaking a bond with water. A classic example is the conversion of ethanol (\(C_2H_5OH\)) to ethene (\(C_2H_4\)) in the presence of a strong acid like sulfuric acid. This reaction produces water (\(H_2O\)) as a byproduct. This reaction is crucial in organic synthesis, where double bonds are needed. Keep in mind that a catalyst is typically required to increase the efficiency of these reactions.

Hydrolysis Reactions

Hydrolysis involves breaking a bond in a molecule using water. 'Hydro' stands for water and 'lysis' means to break. During this process, a water molecule is used to cleave a bond, incorporating an -OH and -H into the fragments. A classic example is the hydrolysis of esters, such as the conversion of ethyl ethanoate (\(CH_3COOC_2H_5\)) into ethanol and ethanoic acid. Hydrolysis is pivotal in many biological processes, such as digestion, where large molecules like proteins and carbohydrates are broken down into their building blocks. This process can be catalyzed by acids, bases, or enzymes, allowing it to occur more efficiently in different environments.

Solvolysis Reactions

Solvolysis refers to a reaction where the solvent, often water, takes part in breaking down a solute. The term 'solvolysis' is a combination of "solvent" and "lysis." As the solvent does the breaking, it itself becomes part of the products. An example is tertiary butyl chloride (\((CH_3)_3CCl\)) reacting with water to form tertiary butyl alcohol (\((CH_3)_3COH\)).Solvolysis is important in determining the reactivity and breakdown of compounds in solution. Factors like solvent polarity can greatly influence how and how fast these reactions occur. This reaction type is commonly discussed in the context of nucleophilic substitution reactions, where the solvent acts as a nucleophile.

Hydration of Alkenes

Hydration of alkenes is an essential reaction where water is added to an alkene to form an alcohol. In this process,

• an alkene adds a water molecule across its double bond, resulting in the formation of alcohol.

A widely studied example is the hydration of ethene (\(C_2H_4\)), which results in ethanol (\(C_2H_5OH\)). This reaction requires a catalyst, typically sulfuric or phosphoric acid, to proceed efficiently.Hydration reactions are significant in industrial processes, such as the production of ethanol, as they allow for the transformation of simple hydrocarbons into more functional and useful compounds. Importantly, this reaction can be guided by Markovnikov's rule, which helps predict the addition pattern for the water across the double bond.