Organic and Physical Chemistry

What is the reactive intermeidate in the reaction of 1,3 butadiene with <br />HBr which results 1,2 and 1,4 addition?

• an allylic radical
• dienophile
• an allylic carbocation
• bromonium cation

Which of the following are conjugated dienes?

• 3-bromo-2-butene

• 1,2-butadiene

• 1,3-butadiene

• 1,5-pentadiene

What is the thermodynamic product obtained from addition of 1 mole <br />of HBr to 1,3 butadiene?

• 3-bromo-2-butene
• 1-bromo-2-butene
• 4-bromo-1-butene
• 3-bromo-1-butene

Which of the following term describes the mechanism for the Diels-Alder reaction of 3-butene-2-one with 1,3 butadiene?

• electrophilic addition
• electrophilic substitution
• cyclo addition
• nucleophilic addition

Conjugated diene reacts with which among the following to form a cyclohexane?

• Phenol
• Dienophile
• Hexane
• Tribromo phenol

The product formed in Diels-Alder reaction is commonly called as

• Cross linked product
• alkane derivative
• linear product
• Adduct

Identify the correct increasing order of stability of dienes

• cumulated dienes< isolated dienes<<br />conjugated dienes
• conjugated dienes<isolated dienes<cumulated dienes
• isolated dienes<cumulated dienes<conjugated dienes
• none of the above

Which is the most predominant product formed in electrophilic substitution reaction?

• 1,2 addition
• 1,2 addition and 1,4 addition
• 1,4 addition
• all the above

If the heat of hydrogenation is high the stability of dienes are

• High
• Low
• Medium
• Very high

Bond length is high for……..

• Isolated dienes
• Cumulated dienes
• Conjugated dienes
• Akanes