which is true about benzene (heat of hydrogenation)

[wall1two]

does benzene produce a higher or lower heat of hydrogenation than expected? i said benzene gives a lower than expected heat of hydrogenation because it is so stable but they say the opposite. (that it gives a higher than expected)

and also, would The reaction of 1-phenyl-1-propene with HBr give

A) 2-bromo-1-phenylpropane
B) 1-bromo-1-phenylpropane

i say 1 bromo but they say it's A.

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[rodneymoss]

does benzene produce a higher or lower heat of hydrogenation than expected? i said benzene gives a lower than expected heat of hydrogenation because it is so stable but they say the opposite. (that it gives a higher than expected)

and also, would The reaction of 1-phenyl-1-propene with HBr give

A) 2-bromo-1-phenylpropane
B) 1-bromo-1-phenylpropane

i say 1 bromo but they say it's A.

Follow Markonikov's Rule for the Halohydrogrenatin reaction. Br will bond to the more substituted carbon of the double bond. The carbon with the least amount of Hydrogens,

 

[loveoforganic]

does benzene produce a higher or lower heat of hydrogenation than expected? i said benzene gives a lower than expected heat of hydrogenation because it is so stable but they say the opposite. (that it gives a higher than expected)

and also, would The reaction of 1-phenyl-1-propene with HBr give

A) 2-bromo-1-phenylpropane
B) 1-bromo-1-phenylpropane

i say 1 bromo but they say it's A.

Heats of hydrogenation are negative, so a "higher" heat of hydrogenation means your reactant was more stable.

 

[NewBee12]

It gives a Lower heat of hydrogenation. The " savings " in energy is called Resonance energy !!!!!!! It would give 1-phenyl-1 bromopropane. First, add an H to the Carbon that would give the most stable carbocation.......this would be C-2.....then attack with the Br-.

good luck

 

[znny19]

it gives you a higher heat of hydrogentation because by hydrogenating the benzene you are disrupting the aromaticity that allows the molecule to be stable.