topic 10 and 20 Flashcards
what evidence suggested against the model by kebulé
- bond angles and bond lengths are all equal
- number of isomers
- no addition rxns
- enthalpy of hydrogenation was less exothermic
what type of reaction do you get from benzene
substitution
no. of delocalized e- in benzene
6
what does benzene react with
electrophiles
what does an optically active compound do
rotate the plane of polarized light as it passes through a solution of the compound
which types of isomers are always optically active
enantiomers
what are enantiomers
non-superimposable images of each other
racemic mixture
a mixture containing both enantiomers in equal amounts and it is optically inactive
outline the formation of nitrobenzene
conc h2so4 and hno3 to form the catalyst (NO2+) which is attracted to the high e- density of delocalized pi bonds of benzene. the e- go to form a bond with the electrophile, but H is still bonded, so the delocalized pi system is partially broken and has a partial positive charge. the intermediate then loses the H+ and the e- from the C-H bond restore the delocalized pi system
conditions for nitrobenzene formation
heat under reflux at 50 deg C to overcome the high Ea, conc h2so4 and hno3
outline what an arene compound is
hydrocarbon with alternating double and single bonds forming rings
outline how nitrobenzene is converted to phenylamine
- reduction, Sn and conc.HCl, to produce the phenylammonium ion C6H5NH3+
2.free the NH2 group by deprotonating the ion by reacting it with NaOH (aqueous)
why doesnt benzene readily undergo addition reactions
an addition reaction would destroy the delocalized system and the stability associated with it
resonance stability energy
delocalization of electrons, as opposed to alternate single and double bonds, leads to increase in stability
chlorination of benzene
AlCl3 catalyst in dry ether to form chlorobenzene
conditions for OH as a nucleophile
heat, NaOH (aq)
conditions for Nh3 as a nucleophile
conc. NH3, heat in a sealed tube
product of a halogenoalkane and NH3
amine + HX
what can the product of NH3 nucleophilic substitution do,
act as another nucleophile and react with more reactant to produce a secondary amine (diethylamine)
conditions of CN- as a nucleophile
KCN (aq), methanol, heat under reflux
in industry, what is the purpose of reacting potassium cyanide with bromoethane
to increase the carbon chain length
why is sn1 a faster reaction than sn2
the formation of the transition state in sn2 is thought to have higher activation energy than the formation of the carbocation in sn1
molecularity
number of molecules that take part in the rate determining step
why cant tertiary alcohols undergo oxidation
the cabron attached to the OH group is fully substituted and is not attached to any H’s
what is the observed color change for the oxidizing agent in nucleophilic addition
orange to green
what is the change in oxidation state for the oxidizing agent (acidified potassium dichromate)
+6 to +3
explain why alcohols have a higher melting and boiling point than alkanes of similar Mr value
similar Mr value means that the alcohol and alkane will have a similar number of e- therefore similar London forces; BUT alcohols also have hydrogen bonds which require more energy to overcome
