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    1.) Explain briefly why benzene does not generally behave chemically like an alkene.

    2.) The conditions for hydrogenating benzene to cyclohexane involve using a catalyst at 300 degrees C and 30 atm. Are these conditions those you would expect? Explain your reasoning?

    Would really appreciate TSR help!

    xx
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    give us your thoughts so far and we'll set you straight. Why do you think benzene might not behave like an alkene? What is similar/different between benzene and alkenes?

    You'll need to have a bash at this yourself first (as per the rules of the forum). Then we can help
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    (Original post by Plato's Trousers)
    give us your thoughts so far and we'll set you straight. Why do you think benzene might not behave like an alkene? What is similar/different between benzene and alkenes?

    You'll need to have a bash at this yourself first (as per the rules of the forum). Then we can help
    Well, I was thinking that the delocalisation of electrons in the benzene ring would make the the bonds within in benzene less reactive in comparison to isolated double bonds. Therefore it would react more like a saturated compound... it wouldn't be very susceptible to addition reactions as these would decrease its delocalisation energy...

    hehe probably not right...
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    (Original post by emilylott)
    1.) Explain briefly why benzene does not generally behave chemically like an alkene.

    2.) The conditions for hydrogenating benzene to cyclohexane involve using a catalyst at 300 degrees C and 30 atm. Are these conditions those you would expect? Explain your reasoning?

    Would really appreciate TSR help!

    xx

    1) Benzene does not behave like an alkene as an alkene has localised electrons concentrated between the carbon atoms only providing alkenes with a high electron density. However, benzene has delocalised electrons spread over all 6 carbons so there is not enough electron density to attract an oncoming molecule such as bromine.

    2) Im not sure about this one.. i've not come across catalysts for hydrogenation of benzene. Just that benzene was hydrogenated to compare with alkene when proving Kekules model incorrect.

    Hope that helped
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    (Original post by emilylott)
    Well, I was thinking that the delocalisation of electrons in the benzene ring would make the the bonds within in benzene less reactive in comparison to isolated double bonds. Therefore it would react more like a saturated compound... it wouldn't be very susceptible to addition reactions as these would decrease its delocalisation energy...

    hehe probably not right...
    no, actually that is pretty much the right answer. The delocalisation makes the benzene ring much less reactive than an alkene. But it also makes it susceptible to substitution reactions (unlike the additions that characterise alkenes). The delocalised pi-electrons in the benzene ring give it such stability that it is more favourable for it to substitute, than to lose all that stability by addition reactions (which would of course turn it into an alkene)

    The second part of the question is related to this too. Hydrogenation of benzene is harder, because the benzene ring is so stable (compared to alkennes)
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    why did I get a negative rep? was actually helping someone out whoever gave it!!!
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    (Original post by Rosi M)
    why did I get a negative rep? was actually helping someone out whoever gave it!!!
    I imagine it was because Plato had suggested that the OP have a go first (as per the forum's norms) and then you upped and just wrote the answer anyway...
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    I think we have a troll here. The OP seems to have been negged too :-/

    No need for that.
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    (Original post by charco)
    I imagine it was because Plato had suggested that the OP have a go first (as per the forum's norms) and then you upped and just wrote the answer anyway...
    so wierd!
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    (Original post by Rosi M)
    1) Benzene does not behave like an alkene as an alkene has localised electrons concentrated between the carbon atoms only providing alkenes with a high electron density. However, benzene has delocalised electrons spread over all 6 carbons so there is not enough electron density to attract an oncoming molecule such as bromine.
    I didn't neg you, but I can sort of see why someone would; the OP's answer was pretty much spot on. I'd say the question's looking for a comment regarding substitution/addition wrt benzene and alkenes. Benzene's electron cloud is situated above and below the carbons so its attraction to electrophiles shouldn't really change (that) much.
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    (Original post by GlibByNature)
    I didn't neg you, but I can sort of see why someone would; the OP's answer was pretty much spot on. I'd say the question's looking for a comment regarding substitution/addition wrt benzene and alkenes. Benzene's electron cloud is situated above and below the carbons so its attraction to electrophiles shouldn't really change (that) much.
    I seeee
 
 
 
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