o chem– halogenoalkanes and alcohols
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primary halogenoalkanes have ____ alkyl group bonded to the halogenated carbon atom
one
why do halogenoalkanes have higher boiling points than similar alkanes?
• halogenoalkanes have net dipole moment -> pd-pd • thus more energy req to overcome -> higher b.p.
what is the trend of b.p down the homologous series
increases
why does the b.p. of halogenoalkanes increase down the homologous series?
• electron cloud size ↑ • more polarisable • strength of LDF ↑ -> energy required ↑ • ↑ b.p.
the b.p. of halogenalkanes down the halogen grp _________ (changes how?)
increases
why does the b.p. of halogenoalkanes increase down the halogen grp?
• electron cloud size ↑ • more polarisable • LDF ↑ -> energy required ↑ • ↑ b.p.
why are halogenoalkanes/arenes generally insoluble in water
the energy released from dp-dp interactions btw halogenoalkanes/arenes + water is insufficient to overcome H bonding in water
why are halogenoalkanes/arenes generally soluble in non polar organic solvents?
the energy released from LDF in halogenoalkanes/arenes + non polar solvent is sufficient to overcome dp-dp btw halogenoalkanes + LDF btw solvent
what are nucleophiles? (short defin.)
electron-rich species that possesses at least one lone pair of e- which can react w e- deficient centres
nucleophile can either be _______ or __________ charged
neutral, negatively
nucleophilic substitution of halogenoalkanes produce…
alcohols
what are the conditions for nucleophilic substitution of halogenoalkanes?
heat under reflux
_______ halogenoalkanes undergo Sn2
primary
secondary halogenoalkanes undergo _______
Sn1 and Sn2
________ halogenoalkanes undergo Sn1
tertiary
what order of reaction is Sn2?
second order
why is Sn2 second order? (understand)
the ROR of the RDS depends on concentrations of the nucleophile and the halogenoalkane
why is Sn1 first order? (understand)
the ROR of the RDS depends on the concentration of the halogenoalkane only
when is the Sn2 mechanism favoured?
when the halogenoalkanes have low steric hindrance
if the final product contains a chiral carbon, there will be an _______ of the stereochemistry
inversion
why does the Sn2 mechanism result in an inversion of the reactant?
• nucleophile attacks halogenoalkane from the back side • product undergoes inversion of configuration
which mechanism for the reaction of halogenoalkanes is one step?
Sn2
draw out the Sn2 mechanism for the reaction of NaOH with bromoethane
-
draw the energy profile diagram for Sn2 mechanism
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