Question

6. Build the cyclobutane ring and study the angle strain and torsional strain. Draw the structures to explain these factors. 7. The conformation of cyclobutane is slightly folded. Folding gives partial relief from the eclipsing of bonds, as shown in the Newman projection. Compare this actual structure with the hypothetical planar structure. Draw the relevant structures. 8. trans-1,2-Dimethylcyclobutane is more stable than cis-1,2-dimethylcyclobutane, but cis-1,3- dimethylcyclobutane is more stable than trans-1,3-dimethylcyclobutane. Use the molecular models to find the reasons for these observations. Also use drawings to explain these observations. 9. Build the cyclopentane ring and study the angle strain and torsional strain in the ring. Draw the structures to explain these factors. Cyclopentane actually assumes a slightly puckered "envelope" conformation that reduces the eclipsing and lowers the torsional strain. Convince yourself about this fact. Provide the relevant drawings. 10. Build the cyclohexane ring and study the angle strain and torsional strain. Build the chair and boat conformations and identify the axial and equatorial bonds. Also identify the "flagpole hydrogens" in the boat conformation. Also study the half-chair and twist-boat conformations. Prove that the half-chair is the least stable of all conformations and twist- boat is more stable than the boat conformation. Provide the relevant drawings/structures.

Answer 1

TH * cyclobutane Each carbon atan of cyclobutane is sp3 hybridised i.e. bond angle of each c-aturn should be 109°28' But the angle is a clobutane is 90° So the strain in the angle is (1098281-90°) = 19°281 In cyclobutane fl-ataus are eclipsing so it generates more strains. To be reduce this strain cyclobutane strabilized through beut conformation. This tratan H-atan repulsion in Cyclobutane is called torsional strain Hypothetical planar structure of cyclobutane in Newman projection HH H HH eclipsed eclipsed tahun H-atom To setie relief this torsional strain the actual cyclobutane formbeut strectuce KH CH3 rent le bit Laviate from eclipsed stabills traus as HH H trans cis har dy cyclobane (1,3-di subtuted methyl group it relaxes. So cis is stable,

H If cyclopentane plauan each angle should be logo, but the nath the latan eclipsed. To reduce the eclipsed stain puchered conformation is for cyclopentane y equiatarial In planer cyclonekane angle sharia and torsional torsional strain present. Angle strain (1090-28-60) = 49°28' Torsional strain is due to the etlipsed H-athing. axialbena H pag material #H chair confirmation Boat confamation twist boat batterior conformation & halt chain confumation In half chain conformation all H-aton are eclipsed except one position so that it is the least stable of all confermatter, and in the twosh boat enformation all thatons are little relaxed randomly. So that it is the most stable confirmation.

chair Boat Between chair and Boat conformation Chan conformation is most stable. 1,3-diaxial L inferation Ethyl cyclobecane 3risopropy 1-1, 1-dimethyl cyclohexane I is most stable an the CH3 Chh egutorial-acial same energy thy scial equatent 4 -chz LCH3 Cruz Stability (1) equatrial equation (6 Trans ) is more stable

uz same energy both same enegy both (C) Traus isomer is moch stable.