benzene chemistry Flashcards
what was the conflicting evidence of kekule’s model that led to the delocalised model being developed.
benzene does not decolourise bromine water
all c-c bonds are the same length
the enthalpy hydrogenation is less exothermic than expected (would expect triple, 3 double bonds)
what word is used to identify the presence of a benzene ring if attached to a chain of 7 or more carbons. What are the 3 exceptions
phenyl
benzoic acid
phenylamine
belnzaldehyde
why can cyclohexene polarise electrophiles
the Pie bond is localised, therefore is a region of high electron density, able to polarise electrophiles.
does benzene react by electrophilic addition + give reasons why
no, the electron density of the pie ring is too low to induce a dipole in electrophiles
benzene can react with halogens in the presence of a catalyst, what is the catalyst, what is the equation for the formation of the electrophile Br-
catalyst - AlBr3 / AlCl3
AlBr3 + Br2 —> AlBr4 - + Br+
benzene can react in a nitration reaction, what is the catalyst, write the formation of the electrophile.
Conc. H2SO4
HNO3 + H2SO4 —> H2O + NO2+ + HSO4 -
What is the catalyst for a Friedal Craft reaction - alkylation
AlBr3
what is the catalyst for a friedal craft reaction - acylation
What small end product is made
FeCl3
HCl
do alcohols react with bases
no
does phenol react with a strong base, if so what product does it make
yes, makes a salt + water
why is phenol more reactive than benzene
the lone pair on oxygen is delocalised into the pie ring
this increases the electron density of the pie ring
able to polarise electrophiles
what kind of directing group is NH2
2,4
what kind of directing group is OH
2,4
what kind of directing group is NO2
3
why is NO2 an electron withdrawing group
the nitrogen does not have a lone pair of electrons so this decreases the electron density in the pie ring making it less able to polarise electrophiles.
