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chemistry - ch. 6 organic chemistry 1 > 6.3 halogenoalkanes & alcohols > Flashcards

6.3 halogenoalkanes & alcohols Flashcards

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1
Q

name the prefixes of Cl, F, Br, I

A

chloro, fluoro, bromo, iodo

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2
Q

describe primary, secondary & tertiary halogenoalkanes / alcohols.

A

primary - at end of carbon chain
secondary - the bonded carbon is bonded to 2 other carbons
tertiary - the bonded carbon is bonded to 3 other carbons

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3
Q

what state is halogenoalkanes usually at?

A

colourless liquid

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4
Q

which 3 halogenoalkanes are gases at room temperature?

A

chloromethane, bromoethane, chloroethane

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5
Q

which will have a higher boiling point, the parent alkane or the halogenoalkane? explain why.

A
  • halogenoalkane
  • polarity of C-X bond leads to stronger intermolecular forces
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6
Q

describe the solubility of halogenoalkanes in water.

A

sparingly soluble, since dipole-dipole forces are much weaker than hydrogen bonding in water

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7
Q

how is halogenoalkanes prepared from alkanes?

A
  • free-radical substitution under heat / UV light
  • halogen atom replaces hydrogen atoms
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8
Q

how is halogenoalkanes prepared from alkenes?

A
  • addition of hydrogen halide / halogen elements to form halogenoalkanes with 1/2 halogens
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9
Q

how is halogenoalkanes prepared from alcohols?

A

react with phosphorus/hydrogen halides

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10
Q

In which 4 ways could halogenoalkanes react by nucleophilic substitution?

A
  • water
  • hydroxide ions
  • cyanide ions
  • ammonia
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11
Q

what conditions are needed for the hydrolysis of halogenoalkanes with water? what is the result?

A
  • with silver nitrate in ethanol
  • forms silver halide (precipitate)
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12
Q

what conditions are needed for the nucleophilic substitution of halogenoalkanes with hydroxide ions?

A
  • warm aqueous alkali
  • under reflux
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13
Q

what conditions are needed for the nucleophilic substitution of halogenoalkanes with cyanide ions?

A
  • warm ethanolic potassium cyanide
  • under reflux
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14
Q

what is the prefix for cyanide compounds?

A

nitriles

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15
Q

what conditions are needed for the nucleophilic substitution of halogenoalkanes with ammonia?

A

excess ethanolic ammonia
heat under pressure in sealed tube

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16
Q

what are the product of ammonia reacted compounds?

A

(primary) amines

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17
Q

what are the products of elimination of halogenoalkanes with hydroxide ions?

A
  • alkenes
  • halide ion
  • water
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18
Q

what are the conditions of elimination of halogenoalkanes with hydroxide ions?

A
  • hot ethanolic alkali
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19
Q

describe the difference in boiling point of the alcohol and its parent alkane.

A

higher boiling point since the hydrogen bonding in -OH is stronger than London forces in alkanes

20
Q

which 2 alcohols are liquids are room temperature?

A

ethanol & methanol

21
Q

what does complete combustion of alcohols produce?

A

CO2 + H2O

22
Q

what is a nucleophile?

A

species that donate a lone pair of e- to form a covalent bond with an electron-deficient atom

23
Q

what does the hydroxide ion act as in an elimination reaction?

A

base

24
Q

rank in order of time taken in terms of tertiary, secondary & primary halogenoalkanes during hydrolysis.

A

tertiary < secondary < primary

25
Q

explain in terms of bond enthalpy the trend in reactivity of iodo-, bromo-, chloro- alkanes.

A

C-I bond has the weakest bond enthalpy so therefore breaks most easily.

26
Q

what is formed in partial oxidation by acidified potassium dichromate of primary alcohols?

A

aldehyde + H2O

27
Q

what is the general formula of an aldehyde?

A

R-CHO

28
Q

what is formed in the full oxidation by acidified potassium dichromate of primary alcohols?

A

carboxylic acids

29
Q

what is the general formula of a carboxylic acid?

A

R-COOH

30
Q

what is the prefix name with an aldehyde?

A

-nal

31
Q

what reagents are required in oxidation of primary alcohols?

A

[O] oxidising agent

32
Q

what is removed from an alcohol that forms an aldehyde?

A

H from OH and another H that is attached to the same carbon

33
Q

what is formed in the oxidation of secondary alcohols?

A

ketone

34
Q

what is the prefix name of ketones?

A

-one

35
Q

in aldehydes, carboxylic acids & ketones which 2 don’t require naming carbon chain positions?

A

carboxylic acids & aldehydes

36
Q

what is formed in elimination of alcohols with concentrated phosphoric acid?

A

alkenes + H2O

37
Q

what are the observations on reacting Na & alcohols?

A
  • effervescence
  • mixture gets hot
  • sodium dissolves
  • white ppt produced
38
Q

how is chloroalkanes formed from alcohols?

A

PCl5 / PCl3 / conc. HCl / mixture of NaCl + H2SO4

39
Q

what is the reaction with PCl5 with alcohols?

A

white / misty fumes of HCl

40
Q

how is bromoalkanes formed with alcohols?

A

potassium bromide (KBr) + 50% concentrated H2SO4

41
Q

how is iodoalkanes formed with alcohols?

A

PI3 (produced in situ with red phosphorus & iodine)

42
Q

why couldn’t tertiary alcohols be oxidised by potassium dichromate?

A

there’s not hydrogen atoms bonded to the carbon with the -OH group attached

43
Q

what tests are used to distinguish aldehydes & ketones?

A

Fehling’s solution / Benedict’s solution

44
Q

what is the reaction & observation with aldehydes and Fehling’s solution?

A

aldehydes are oxidised into carboxylic acids & Cu2+ ions are reduced into copper(I) oxide

blue Cu2+ ions change into brick-red precipitate of copper(I) oxide

45
Q

what is used to test for a carboxylic acid?

A

addition of sodium carbonate; effervescence

46
Q

why is ethanol and excess NH3 needed in nucleophilic substitution of halogenoalkanes to amines?

A

ethanol: solvent for organic compounds
excess NH3: neutralises acid produced (H+)

chemistry - ch. 6 organic chemistry 1 (4 decks)

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