The conformation of cyclopentane is to be analysed considering the structure to be planar and the torsional strain is to be calculated. Concept introduction: Cyclopentane was predicted by Baeyer to be nearly strain-free, but it actually has total strain energy of 26 kJ/mol. planar cyclopentane has practically no angle strain, it has a large torsional strain. Cyclopentane therefore twists to adopt a puckered, nonplanar conformation that strikes a balance between increased angle strain and decreased torsional strain. Four of the cyclopentane carbon atoms are in approximately the same plane, with the fifth carbon atom bent out of the plane. Most of the hydrogens are nearly staggered with respect to their neighbours.

Question

Estimate the heat released when ethene(CH2=CH2) reacts with HBr to giveCH3CH2Br. Bond enthalpies areC-H : 412 kJ/mol; C-C : 348 kJ/mol;C=C : 612 kJ/mol; C-Br : 276 kJ/mol;Br-Br : 193 kJ/mol; H-Br : 366 kJ/mol. Choose the correct answer:1. 1036 kJ/mol2. 58 kJ/mol3. 424 kJ/mol4. 200 kJ/mol5. 470 kJ/mol

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Question

Chapter 4.4, Problem 10P

Interpretation Introduction

Interpretation:

The conformation of cyclopentane is to be analysed considering the structure to be planar and the torsional strain is to be calculated.

Concept introduction:

Cyclopentane was predicted by Baeyer to be nearly strain-free, but it actually has total strain energy of 26 kJ/mol. planar cyclopentane has practically no angle strain, it has a large torsional strain. Cyclopentane therefore twists to adopt a puckered, nonplanar conformation that strikes a balance between increased angle strain and decreased torsional strain. Four of the cyclopentane carbon atoms are in approximately the same plane, with the fifth carbon atom bent out of the plane. Most of the hydrogens are nearly staggered with respect to their neighbours.

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Estimate the heat released when ethene(CH2=CH2) reacts with HBr to giveCH3CH2Br. Bond enthalpies areC-H : 412 kJ/mol; C-C : 348 kJ/mol;C=C : 612 kJ/mol; C-Br : 276 kJ/mol;Br-Br : 193 kJ/mol; H-Br : 366 kJ/mol. Choose the correct answer:1. 1036 kJ/mol2. 58 kJ/mol3. 424 kJ/mol4. 200 kJ/mol5. 470 kJ/mol

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