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Chemistry > halogenoalkanes > Flashcards

halogenoalkanes Flashcards

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1
Q

how to form a chloroalkane from an alcohol

A

dry PCl5 (or conc HCl)
room temperature

nucleophilic substitution

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2
Q

how to form a bromoalkane from an alcohol

A

KBr + conc H2SO4
heat under reflux
nucleophillic substitution (HBr attacks)

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3
Q

how to form a iodoalkane from an alcohol

A

damp red phosphorus + I2
warm
nucleophilic substitution

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4
Q

how to form an alkene from a halogenoalkane

A

conc KOH or conc NaOH
in ethanol
heat under reflux
elimination reaction

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5
Q

how to form an amine from a halegenoalkane

A

NH3 (ammonia)
heat in a sealed tube in ethanol
nucleophilic substitution

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6
Q

how to form an alcohol from halogenoalkane with water

A

add H2O
warm
ethanol co solvent

nucleophilic substitution

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7
Q

how to form a nitrile from a halogenoalkane

A

KCN
in ethanol
heat under reflux
nucleophilic substitution

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8
Q

what is a nucleophile

A

chemical species with a lone pair of electrons (can donate electrons)

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9
Q

define substitution reaction

A

where one atom or group of atoms is replaced by another atom or group of atoms

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10
Q

why are the C-halogen bonds easier to break going down the group

A

bond length increases
weaker bond
broken faster

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11
Q

how to form an alcohol with halogenoalkane and aqueous alkali

A

dilute NaOH or KOH (aqueous)
ethanol co solvent
heat (60°)

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12
Q

which mechanism do tertiary halogenoalkanes react by

A

SN1

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13
Q

which mechanism do primary halogenoalkanes react by

A

SN2

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14
Q

which mechanism has the transition state

A

SN2 (primary halogenoalkanes)

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15
Q

what colour ppt Cl

A

white

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16
Q

what colour ppt Br

A

cream

17
Q

what colour ppt I

A

yellow

18
Q

order in which halogenoalkane ppt appears

A

1 Iodo
2 Bromo
3 Chloro

19
Q

order ppt appears (1° 2° or 3°)

A

1 3°
2 2°
3 1°

20
Q

why does the 3° react faster than 1° with water

A

weak nucleophile
mechanism is SN1

21
Q

devise an experiment to compare rates of hydrolysis of halogenoalkanes

A
  • 3 test tubes with each halogenoalkane
  • warm water bath, reach same temperature
  • ethanol as co solvent
  • add silver nitrate
  • time how long each takes to produce ppt
22
Q

state trends in rate of reaction and justify answer (hydrolysis of halogenoalkanes)

A

iodo>bromo>chloro
bond enthalpy decreases from C-Cl to C-I
bonds become easier to break down the group

23
Q

define elimination reaction

A

reaction where an atom or group of atoms is removed from a molecule
leaves an unsaturated product

24
Q

when forming an alkene from a halogenoalkane, which carbon is the hydrogen removed from

A

the C adjacent to the C the halogen is bonded to
not the same C the halogen is bonded to

Chemistry (31 decks)

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