Addition Reaction Important Questions Chemistry

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Very Short Answers Type Questions (1 mark)

Ques. What is an addition reaction in organic chemistry?

Ans. A chemical reaction in which two or more small compounds react together to form a larger molecule is called an addition reaction. Only unsaturated compounds participate in this type of reaction. 

Ques. What are the examples of addition reactions?

Ans. Examples of addition reactions include:

• Halogenation
• Hydration 
• Polymerization 
• Hydrogenation 

Ques. What do you understand about electrophiles? 

Ans. Species that accept electrons are called electrophiles. Carbocations and carbonyl compounds are examples of electrophiles. 

Ques. What is the anti-markonikov’s rule in addition reaction?

Ans. When an alkene interacts with a nucleophile, the anti-Markovnikov rule states that the hydrogen atom will be bonded to the more reduced carbon and the nucleophile will be bound to the less reduced carbon. 

Ques. What are the different types of addition reactions?

Ans. Addition reactions are broadly classified into four types:

• Electrophilic addition reactions 
• Nucleophilic addition reactions 
• Free-radical addition reactions
• Cycloaddition reactions 

Ques. What are the important factors that affect the rate of addition reactions?

Ans. The rate of addition reaction depends on the four important factors; 

• Solvent effects
• Catalysts
• Nature of reactants
• Temperature

Ques. Which type of compounds are mainly involved in addition reactions?

Ans. Unsaturated hydrocarbons containing two or more bonds that can be easily broken and bonded to other molecules, such as alkenes or alkynes, are the basis for addition reactions.

Ques. Can alkanes participate in addition reactions?

Ans. Alkanes cannot participate in this kind of reaction because they have only single covalent bonds and don't have the functional groups required for addition reactions.

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Short Answers Type Questions (2 marks)

Ques. Are nucleophiles used in addition reactions? 

Ans.  Nucleophiles are species that are capable of donating their electrons. Based on their capacity, nucleophiles are divided into two categories: strong and weak nucleophiles. Strong nucleophiles such as R–MgX do not require any catalyst to initiate the reaction whereas weak nucleophile such as water uses acid as a catalyst. Ammonia and water are the two common examples of nucleophiles.

Ques. What do you understand about major and minor products in the reaction?

Ans. Major and minor products are formed in the case of asymmetrical hydrocarbons (with two different groups). 

• The carbocation that is stable and present in larger quantities is called a major product. 
• The carbocation intermediate product that is not as stable as the major product and is present in a lesser quantity is called a minor product. 

Ques. What is the effect of catalysts in the addition reactions?

Ans. A catalyst is a substance that regulates the rate of reaction. It either accelerates or decelerates the rate of a chemical reaction. 

• Usually, acids or bases act as catalysts in the addition reactions. 
• In acid-catalyzed reactions, the electrophile becomes stronger.

Ques. What is the markonikov’s rule in addition reaction?

Ans. The unsaturated carbonyl compounds such as alkenes or alkynes follow a rule called markonikov’s rule. 

• In this case, carbocation is formed as an intermediate product. 
• The rule states that in the reaction of protic acid (HX) with an asymmetric alkene, the negative (halide) group is attached to a carbon atom having a higher number of alkyl substituents whereas the positive group is attached to carbon with a lower number of alkyl substituents. 

Ques. What is an aldol condensation reaction?

Ans. The reaction of an enolate ion with a carbonyl compound gives either beta-hydroxy ketone or beta-hydroxy aldehyde in the presence of a catalyst such as acid or base. This reaction is called the aldol condensation reaction. 

Ques. What do you understand about hydration reaction?

Ans. Hydration is a common example of an addition reaction in which water is involved. This process is generally utilized for the preparation of alcohol. 

• The reaction is proceeded by the addition of alkene with water in the presence of a catalyst (Conc. H2SO4). 
• The chemical reaction is expressed as: 

R–CH=CH₂ + H₂O ➡ R–CH(OH)–CH₃

Ques. What is a free radical addition reaction?

Ans. An atom, molecule, or ion that has at least one pair of unpaired electrons is called a free radical. 

• The reaction in which free radicals are added to unsaturated substrates to form a new covalent bond is called the free radical reaction. 
• The reaction follows abri-markonikov’s rule. 

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Long Answers Type Questions (3 marks)

Ques. What is the cycloaddition reaction?

Ans. A type of addition reaction in which a ring is formed as a final product is called a cycloaddition reaction. The formation of cyclohexane by the reaction of 1,3-butadiene with ethene is an example of cycloaddition. 

(1,3-Butadiene + Ethene → Cyclohexane)

Ques. What are the applications of addition reactions? 

Ans. Addition reactions have several applications in organic chemistry such as: 

• The reaction is utilized in the purification of aldehydes. 
• Alcohols can be converted into alkenes with the help of addition reactions.
• This reaction can also be utilized for industrial purposes such as in the hydrogenation of oils, polymers (PVC) formation, and the synthesis of biopharmaceuticals. 

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Very Long Answers Type Questions ( 5 marks)

Ques. What is the reaction mechanism of the nucleophilic addition reaction? 

Ans. The nucleophilic addition reaction occurs in two steps: 

Step- 1 Attack of Nucleophile 

This is the first step of the reaction in which the interaction of electrophilic C=O with nucleophile takes place. 

• This is followed by the hybridization of the carbonyl group from Sp² to Sp³. 
• Tetrahedral alkoxide intermediate product is formed in this step. 

Step-2 Addition Reaction

The alkoxide gets protonated by the addition of acids and forms alcohol as a product.

• Now, in the presence of a Grignard reagent (R–MgX) which is a strong nucleophile, an intermediate is formed by the attack on C=O. 

Ques. How do addition reactions differ from substitution reactions?

Ans. The main differences between addition reactions and substitution reactions are as follows: