Free radicals

28 questions on Free radicals from the General Organic Chemistry III: Reaction Intermediates chapter: 6 NEET level, 11 JEE Main, 11 JEE Advanced. Each one opens with its answer and solution.

• Which of the following free radicals is the most stable? NEET level
• Homolytic fission of a covalent bond A-B gives NEET level
• The methyl radical CH3^. is best described as NEET level
• Which of the following can be used to start a free radical chain reaction on heating? NEET level
• Propene reacts with HBr in the presence of an organic peroxide to give mainly NEET level
• In the chlorination of methane in light, which step is a chain-terminating step? NEET level
• Arrange the radicals (a) CH3^., (b) CH3CH2^., (c) (CH3)2CH^. and (d) CH2=CH-CH2^. in decreasing order of stability. JEE Main level
• Cyclohexene is treated with N-bromosuccinimide (NBS) in CCl4 in the presence of light. The major organic product is JEE Main level
• Count only constitutional isomers (ignore stereoisomers). The number of different monochloro products obtainable from 2-methylbutane by free radical chlorinatio... JEE Main level
• Neopentane (CH3)4C is allowed to react with Cl2 in the presence of light, and only monochlorination is considered. The product obtained is JEE Main level
• The number of alpha C-H bonds that can take part in hyperconjugation in the 2-methylbutan-2-yl radical CH3-C^.(CH3)-CH2-CH3 is JEE Main level
• 2-Methylpropene reacts with HBr in the presence of a peroxide. The major product is JEE Main level
• The peroxide (anti-Markovnikov) effect is observed with HBr but not with HCl or HI because JEE Main level
• Arrange the radicals (a) (C6H5)3C^., (b) C6H5CH2^., (c) (CH3)3C^. and (d) CH3^. in decreasing order of stability. JEE Main level
• Ethylbenzene reacts with bromine in the presence of light (side-chain radical bromination). The major monobromo product is JEE Main level
• Which of the following are propagation steps in the free radical monochlorination of methane? JEE Main level
• Free radical monochlorination of 2-methylbutane is carried out at room temperature. Take the relative reactivities per hydrogen for 1 deg : 2 deg : 3 deg C-H as... JEE Main level
• Count every stereoisomer (enantiomers counted separately) as a different product. The total number of monochlorination products that can be formed by free radic... JEE Advanced level
• Optically pure (S)-3-methylhexane is treated with Br2 in light. The major monobromo product, 3-bromo-3-methylhexane, is obtained as JEE Advanced level
• Which of the following C-H bonds has the lowest bond dissociation energy? JEE Advanced level
• 3-Methylbut-1-ene reacts with HBr (i) in the dark in a polar medium, and (ii) in the presence of a peroxide. The major products are, respectively, JEE Advanced level
• In the monochlorination of 2,3-dimethylbutane the relative reactivity per hydrogen is 1 deg : 3 deg = 1 : 5. The ratio (moles of 1-chloro-2,3-dimethylbutane) : ... JEE Advanced level
• Use these bond energies in kcal mol^-1: secondary C-H 98, H-Br 88, Br-Br 46, secondary C-Br 71. For the propagation steps of the radical bromination of propane ... JEE Advanced level
• Monochlorination of 2-methylbutane in light is carried out with relative reactivities per hydrogen 1 deg : 2 deg : 3 deg = 1 : 3.8 : 5.0. Stereoisomers of one c... JEE Advanced level
• Which of the following radicals are stabilised by resonance (delocalisation of the unpaired electron over more than one atom)? JEE Advanced level
• Which of the following alkanes give only ONE monochloro product (constitutional isomer) on free radical chlorination? JEE Advanced level
• Which of the following alkenes give a primary alkyl bromide as the MAJOR product with HBr in the presence of a peroxide? JEE Advanced level
• Free radical monobromination of 2,3-dimethylbutane is done with relative reactivities per hydrogen 1 deg : 3 deg = 1 : 1600. Which statements are correct? JEE Advanced level