MCAT Biology : Molecular Properties
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Example Question #4 : Properties Of Hydrocarbons
Which of the following cycloalkanes has the largest amount of ring strain?
Cyclohexane
Cyclobutane
Cyclodecane
Cyclododecane
Cyclobutane
The general trend for ring strain in cycloalkanes is that cyclohexane has zero ring strain. The strain increases as you decrease or increase the ring from six carbons. Strain increases upward until reaching ten carbons, at which point, the strain will decrease toward zero strain as the number of carbons continues to increase.
In general, the highest ring strain will be found in the smallest, most distorted ring. Cyclopropane and cyclobutane have particularly high strain.
Example Question #3 : Properties Of Hydrocarbons
Which of the following molecules has the potential to produce the most energy?
Pentane
Heptene
Hexene
Hexane
Heptane
Heptane
The larger and more saturated a hydrocarbon is, the more potential energy it can produce. More saturation and a longer chain mean that the molecule has more bonds, and is thus storing more energy.
Hydrocarbons can be completely broken down via combustion reactions to produce carbon dioxide and water. Another way to measure the energy is to determine the number of molecules created from a full combustion reaction.
In this question, the largest and most saturated hydrocarbon is heptane; it is fully saturated and has seven carbons. Heptene also has seven carbons, but is not fully saturated.
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