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Quick clarification on the following:
Which is true of the following information found online?
1). Angle strain can be experimentally determined by heats of combustion. Heats of combustion can also be used to rank the relative stabilities of isomers. The higher the heat of combustion for a molecule, the more stable it is. For example, cyclopropane has a heat of combustion of roughly 500 kcal/mol compared to cyclohexane at 945 kcal/mol. This exceptionally high difference is due to the fact that cyclohexane can conform in such a way so as to alleviate angle strain. This is known as the chair conformation of cyclohexane.
2). Combustion must be due to the energy state of the original hydrocarbon before combustion takes place. The lower the Heat of Combustion per carbon in the molecule the lower the energy state of the initial hydrocarbon whose stability we are comparing. For example, cyclopropane has a Heat of Combustion per carbon of 166.6 kcal/mol. This is compared to cyclobutane with 164.0 kcal/mol, cyclopentane with 158.7 kcal/mol, and cyclohexane with 157.4 kcal/mol. Notice that cyclopropane has the highest Heat of Combustion, and therefore, should be the highest energy state (less stable) of all four cycloalkanes.
In other words, how does stability relate to heat of combustion (general trends)? These data are not in agreement..
Which is true of the following information found online?
1). Angle strain can be experimentally determined by heats of combustion. Heats of combustion can also be used to rank the relative stabilities of isomers. The higher the heat of combustion for a molecule, the more stable it is. For example, cyclopropane has a heat of combustion of roughly 500 kcal/mol compared to cyclohexane at 945 kcal/mol. This exceptionally high difference is due to the fact that cyclohexane can conform in such a way so as to alleviate angle strain. This is known as the chair conformation of cyclohexane.
2). Combustion must be due to the energy state of the original hydrocarbon before combustion takes place. The lower the Heat of Combustion per carbon in the molecule the lower the energy state of the initial hydrocarbon whose stability we are comparing. For example, cyclopropane has a Heat of Combustion per carbon of 166.6 kcal/mol. This is compared to cyclobutane with 164.0 kcal/mol, cyclopentane with 158.7 kcal/mol, and cyclohexane with 157.4 kcal/mol. Notice that cyclopropane has the highest Heat of Combustion, and therefore, should be the highest energy state (less stable) of all four cycloalkanes.
In other words, how does stability relate to heat of combustion (general trends)? These data are not in agreement..
