Chapter 2: Problem 164
When propyne reacts with excess of chlorine water, the product obtained is (a) 1,1 -dichloro propan-2-one (b) 1,1 -dichloropropan-2-ol (c) 2,2 -dichloropropan- 1 -al (d) 1,2 -dichloropropane
Short Answer
Expert verified
Answer: 1,2-dichloropropane.
Step by step solution
01
Write the chemical equation for the reaction
Begin by writing the chemical equation for the reaction of propyne with chlorine water. We have:
Propyne (C3H4) + Cl2 (aq) → Product
02
Determine the most reactive site
In propyne, the carbon-carbon triple bond is the most reactive site, as it can break and form new bonds with incoming atoms (in this case, chlorine). The triple bond consists of one sigma and two pi bonds. During the reaction, one of the pi bonds breaks to form new bonds with the incoming chlorine atom.
03
Apply electrophilic addition
Electrophilic addition occurs when an electrophile (a molecule attracted to electrons) interacts with a nucleophile (a molecule donating electrons). In this reaction, the chlorine molecule (Cl2) acts as the electrophile, and the carbon-carbon triple bond in propyne acts as the nucleophile. The bond between the chlorine atoms breaks, and one chlorine atom forms a bond with each carbon atom of the triple bond. This results in the addition of two chlorine atoms to the propyne molecule, converting it into a vicinal dihalide compound.
04
Identify the correct product
After the electrophilic addition reaction, the product obtained is 1,2-dichloropropane, which corresponds to option (d). The carbon-carbon triple bond converts into a single bond, and each carbon atom involved in the triple bond forms a new bond with a chlorine atom.
So, the correct answer is (d) 1,2-dichloropropane.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Propyne Reaction
Propyne is a hydrocarbon with a triple bond in its structure, making it highly reactive. This molecule is a type of alkyne since it contains the chemical formula C₃H₄. One key characteristic is that the triple bond can participate in various chemical reactions. Propyne's triple bond is composed of one sigma bond and two pi bonds.
In a typical chemical reaction involving propyne, the triple bond is the most reactive site. This is because the pi bonds, which are more exposed than the sigma bond, can easily break and allow for new bonds to form. The reaction with chlorine water is a classic demonstration of this reactivity.
When propyne reacts with an excess of chlorine water, the energy provided by the reaction environment can break one of these pi bonds. The interaction results in the formation of new bonds with the chlorine atoms. Consequently, the triple bond converts into a single bond, forming a more saturated organic compound known as a vicinal dihalide.
In a typical chemical reaction involving propyne, the triple bond is the most reactive site. This is because the pi bonds, which are more exposed than the sigma bond, can easily break and allow for new bonds to form. The reaction with chlorine water is a classic demonstration of this reactivity.
When propyne reacts with an excess of chlorine water, the energy provided by the reaction environment can break one of these pi bonds. The interaction results in the formation of new bonds with the chlorine atoms. Consequently, the triple bond converts into a single bond, forming a more saturated organic compound known as a vicinal dihalide.
Electrophilic Addition
Electrophilic addition is a fundamental reaction mechanism in organic chemistry. It typically occurs with compounds that have multiple bonds, such as alkenes and alkynes, which have higher electron densities. The process involves two primary players: an electrophile and a nucleophile.
An electrophile is a positively charged or electron-deficient molecule, like chlorine, which is attracted to electron-rich areas. In the propyne reaction, the chlorine molecule acts as an electrophile. On the other hand, the nucleophile donates electrons. Here, the carbon-carbon triple bond in propyne serves as the nucleophile.
The reaction proceeds by breaking one of the pi bonds from the triple bond, allowing each of the carbon atoms to bind with a chlorine atom. This type of step forms a new compound by converting double or triple bonds into single bonds, effectively adding atoms to the original molecule. This specific reaction transforms propyne into 1,2-dichloropropane, where the chlorine atoms are attached to adjacent carbon atoms in the compound.
An electrophile is a positively charged or electron-deficient molecule, like chlorine, which is attracted to electron-rich areas. In the propyne reaction, the chlorine molecule acts as an electrophile. On the other hand, the nucleophile donates electrons. Here, the carbon-carbon triple bond in propyne serves as the nucleophile.
The reaction proceeds by breaking one of the pi bonds from the triple bond, allowing each of the carbon atoms to bind with a chlorine atom. This type of step forms a new compound by converting double or triple bonds into single bonds, effectively adding atoms to the original molecule. This specific reaction transforms propyne into 1,2-dichloropropane, where the chlorine atoms are attached to adjacent carbon atoms in the compound.
Chemical Equation
Chemical equations are concise ways of describing chemical reactions. They depict the reactants—the starting substances—and the products formed as a result of the chemical process. For the reaction of propyne with chlorine water, the chemical equation is crucial in predicting the outcome.
In writing the chemical equation for this reaction:
In writing the chemical equation for this reaction:
- Starting Reactants: Propyne (C₃H₄) and Chlorine (Cl₂)
- Reaction Arrow: Indicates the direction from reactants to products
- Products: 1,2-dichloropropane (C₃H₆Cl₂), resulting from the addition of chlorine atoms