The number of isomeric tetraenes (NOT containing $s p$-hybridized carbon atoms) that can be formed from the following reaction sequence is ______.
Correct Answer: 2
Approach Solution - 1
Correct answer is 2
Approach Solution -2
To solve this problem, we need to analyze the given reaction sequence step by step and determine how many isomeric tetraenes (not containing sp-hybridized carbon atoms) can be formed.
1. First Step: Reaction with Sodium in Liquid Ammonia (Na, liquid NH3)
This step represents the Birch reduction, where the benzene ring undergoes partial hydrogenation. This reaction adds hydrogen atoms to the carbon-carbon double bonds in the benzene ring, converting it into a cyclohexadiene intermediate. The product is a 1,4-cyclohexadiene, where two hydrogen atoms are added to the ring in a specific manner.
2. Second Step: Addition of Bromine (Br2, excess)
In the presence of excess bromine (Br2), the cyclohexadiene intermediate undergoes electrophilic addition to the double bonds. Since there are two double bonds, the excess bromine adds across both of them, leading to the formation of a dibromo intermediate. The product of this step is a dibromocyclohexane.
3. Third Step: Reaction with Alcoholic Potassium Hydroxide (alc. KOH)
Alcoholic KOH induces elimination reactions. In this case, the reaction leads to the elimination of HBr from the dibromocyclohexane, resulting in the formation of a conjugated diene. This step can form two isomers due to the positions of the double bonds in the final product, leading to the formation of two isomeric tetraenes (the conjugated dienes).
Conclusion:
From the reaction sequence, two isomeric tetraenes are formed, and neither of them contains sp-hybridized carbon atoms (as no triple bonds are involved).
Final Answer:
The number of isomeric tetraenes that can be formed from the given reaction sequence is 2.
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Hydrocarbons
Hydrocarbons can be described as organic compounds that consists only hydrogen and carbon atoms. These compounds are of different types and thereby have distinct natures. Hydrocarbons are colorless gases and are known for discharging faint odours. These have been categorized under four major classes named as alkynes, alkanes, alkenes, and aromatic hydrocarbons.
Types of Hydrocarbons
- Saturated hydrocarbons - Saturated hydrocarbons are those compounds where there is a single bond exists between carbon atoms and are saturated with atoms of hydrogen.
- Unsaturated hydrocarbons - Hydrocarbons comprises of at least one double or triple bond between carbon atoms are known as unsaturated hydrocarbons.
- Aliphatic hydrocarbons - The term denotes the hydrocarbons formed as an outcome of the chemical degradation of fats. Aliphatic hydrocarbons are basically chemical compounds.
- Aromatic hydrocarbons - They are distinguished because of the presence of benzene rings in them. They give away distinct types of aroma. These hydrocarbons comprises of only hydrogen and carbon atoms.