Organic Chemistry
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Looking at the values of heat of hydrogenation, determine whether cyclohexa-1,4-diene or cyclohexa-1,3-diene is more stable.
What is the reason behind the difference in stability of the given alkenes?
When one equivalent of Br2 reacts with 2,3-dimethylbuta-1,3-diene, two alkene products are formed. Determine which alkene is more stable. Why?
In which of the following pairs of species is the first one more stable than the second one?
Which of the following carbanion species is the most stable?
Rank the following substances in order of increasing stability.
cis-5-decene; (Z)-3,6-diethyloct-4-ene; (Z)-5,6-dimethyldec-5-ene; trans-5-decene
Arrange the following alkenes according to their heat of hydrogenation (From lowest to highest).
Identify which member in each pair is more stable than the other. Also, calculate their energy difference in KJ/mol using the table given below.
A double bond is usually more stable in an endocyclic position of a five-membered ring than in the exocyclic position. Comparing the estimated hydrogenation energies of the two pairs given below.
The first pair shows an energy difference of about 5 KJ/mol while the second pair shows an energy difference of about 9 KJ/mol.
Explain this discrepancy and suggest which number should be trusted under this effect.
Which of the following alkenes are stable, and which ones are unstable? Support your answer with a suitable reason.
a. trans-3,4-dibromocyclopent-1-eneb. 1,2-dibromocyclopent-1-enec. trans-cyclooctened. trans-1,2-dibromocyclopent-1-ene
Predict which one of the given isomers is most stable and which one is least stable.
cis-But-2-ene and trans-but-2-ene have an energy difference of 4 KJ/mol. On the other hand, the trans isomer of 2,2,5,5-tetramethylhex-3-ene has about 40 KJ/mol lower energy than the cis isomer. Explain the reason behind this very high stability of the trans isomer of 2,2,5,5-tetramethylhex-3-ene.
Consider the following alkenes:
Arrange them in order of increasing stability. Justify your order.
(i) Draw a one-step, concerted arrow-pushing mechanism for the formation of (II) from (I).
(ii) Identify which side is favored and justify.
(iii) Identify the product expected to be hydrogenated with a more exothermic heat of hydrogenation.
Determine which is the more stable alkene between alkene X and alkene Y when both produce the same alkane from catalytic hydrogenation, given that the heat of hydrogenation of alkene X is 19.8 kcal/mol, while that of alkene Y is 27.3 kcal/mol.
Given the following pair of alkenes:
Determine which one is (i) the most stable, (ii) the least stable, and (iii) the smallest heat of hydrogenation.
We are given the following alkenes:
2,3-dimethylpent-2-ene, 2,4-dimethylpent-2-ene, and 4,4-dimethylpent-2-ene
Determine which one (i) is the most stable, the one with (ii) the highest, and (iii) the smallest heat of hydrogenation.
Determine which of the given alkenes is the most stable.
Determine which of the given alkenes is the least stable.
Determine which in the following pair of alkenes is more stable.
Using the following data:
(i) Determine the difference in the energy of hydrogenation between 2-methylbut-1-ene and 2-methylbut-2-ene.
(ii) Determine the more stable of the two alkene isomers.
Provide an explanation of the relative stability (stable or unstable) of the given alkene.
Determine which is the most stable and the least stable in the following set of alkene isomers.
Which of the following isomers is expected to be the least stable? The most stable?
In 1935, German chemist J. Bredt proposed that unless one of the rings had at least eight carbons, a bicycloalkene could not have a double bond at a bridgehead carbon. It is referred to as Bredt's rule. Describe why the double bond in the given compound is impossible.