I know that hyperconjugation stabilises a double bond. But in propene an electron-donating group $(\ce{-CH3})$ is increasing the electron density at the double bond, so its nucleophilicity should be higher. How can it be more stable as well as more reactive?
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$\begingroup$ you said more reactive, but with what are you reacting both of them. $\endgroup$– TeslaBoltCommented Feb 12, 2022 at 11:00
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$\begingroup$ @TeslaBolt I meant that propene has higher nucleophilicity than ethene. I am reacting them both with the same electrophile. $\endgroup$– SatyaCommented Feb 12, 2022 at 14:03
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2$\begingroup$ What do you mean by "stable"? $\endgroup$– user55119Commented Feb 12, 2022 at 15:47
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1$\begingroup$ The heats of formation decreases by -5 kcal/mol for every -CH2- group that is added to each homologous. the n-alkanes . This doesn't mean that n-hexane is more stable tha n-pentane. Look here. $\endgroup$– user55119Commented Feb 16, 2022 at 23:15
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1$\begingroup$ I don't say that. Is benzene more stable than cyclohexene in the presence of bromine? Yes, it ia kinetic difference. Is 1,2,4-tri-t-butylbenzene more stable than cyclohexene in in a UV photochemical reaction ? No, the benzene compound absorbs light to form a Dewar benzene and cyclohexene doesn't. Stability is relative to conditions.. $\endgroup$– user55119Commented Feb 17, 2022 at 20:53
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1 Answer
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you need to go with the mechanism.
1st
in this case propene will form a 2nd degree carbocation which is more stable.
2nd
when the electrophile is having a lone pair then a 3 membered ring is formed as intermidiate.then the other Nucleophile attack to open the ring and thus product is formed.
you can refer to Markovnikov's Rule for further info(https://en.wikipedia.org/wiki/Markovnikov%27s_rule)
