CHM136H1 Lecture : Tutorial 4.pdf

• School: UTSG
• Department: Chemistry
• Course: CHM136H1
• Professor: C.Scott Browning

Document Summary

Larger cycloalkanes have more rotational freedom around sigma bonds. Common ring sizes (c3 - c7) are severely restricted in molecular motions. Ring strain - combined angle and torsional strain. Angle strain - the strain induced in a molecule when bond angles are forced to deviate from the ideal 109 . Steric strain - the strain due to repulsive interactions when atoms approach each other too closely. To measure the amount of strain in a compound, measure total energy of compound and subtract energy of strain-free reference compound. Easiest experimental way for cycloalkane is measuring heat of combustion - the more energy released, the more energy the compound has due to strain. Heat of combustion of cycloalkane depends on size, so we must look at the heats of combustion per ch2 unit. Subtracting a reference value from a strain-free acyclic alkane and then multiplying by the number of ch2 units.