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A-level chemistry > Alcohols > Flashcards

Alcohols Flashcards

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1
Q

general formula of alcohols

A

CnH2n+1OH

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2
Q

describe a primary alcohol

A

one carbon is bonded to the carbon on the OH group

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3
Q

describe a secondary alcohol

A

two carbons are bonded to the carbon on the OH group

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4
Q

describe a tertiary alcohol

A

three carbons are bonded to the carbon on the OH group

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5
Q

general equation for reaction with oxygen (combustion)

A

ROH + O2 –> CO2 + H2O

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6
Q

what type of reaction is reactions with halogenoalkanes

A

substitution

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7
Q

Alcohol + phosphorus pentachloride –>

A

chloroalkane

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8
Q

general equation for reaction with phosphorus pentachloride (secondary + primary alcohols)

A

ROH + PCl5 –> RCl + HCl + POCl3

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9
Q

alcohol + hydrochloric acid –>

A

chloroalkane

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10
Q

general equation for reaction with hydrochloric acid (tertiary alcohols)

A

ROH + HCl –> RCl + H2O

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11
Q

alcohol + bromine ions –>

A

bromoalkane

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12
Q

conditions for reaction with bromine ions

A
  • 50% concentrated H2SO4
    (acid catalyst)
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13
Q

equations for reaction with bromine ions

A

KBr + H2SO4 –> HBr + KHSO4
ROH + HBr –> RBr + H2O

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14
Q

Alcohol + phosphorus triiodide –>

A

iodoalkane

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15
Q

equation for making phosphorus triiodide

A

2P + 3I2 –> 2PI3
(red phosphorus + iodine)

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16
Q

general equation for reaction with phosphorus triiodide

A

3ROH + PI3 –> 3RI + H3PO3

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17
Q

name of H3PO3

A

phosphonic acid

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18
Q

what type of reaction forms alkenes

A

elimination

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19
Q

what is needed for an elimination reaction

A
  • concentrated acid catalyst
    (concentrated phosphoric acid- H3PO4)
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20
Q

reaction of ethanol mixed with concentrated phosphoric acid

A

C2H5OH –> CH2=CH2 + H20

21
Q

what products are formed in the reaction with conc phosphoric acid

A

two possible alkenes, depending on what side of the hydroxyl group the Hydrogen is eliminated from

22
Q

how is the reaction with PCl5 a test for alcohols

A

produces white, steamy fumes that can turn damp blue litmus paper red

23
Q

which types of alcohols can be easily oxidised

A

primary and secondary

24
Q

name an oxidising agent

A

acidified potassium dichromate (VI)

25
Q

what are primary alcohols oxidised to (with initial heating)

A

aldehydes

26
Q

what are primary alcohols oxidised to under reflux

A

carboxylic acids

27
Q

equation for oxidation of ethanol (heating)

A

CH3CH3OH + [O] –> CH3CHO + H2O
——————————-ethanal———-

28
Q

equation for reflux of ethanol

A

CH3CHO + [O] –> CH3COOH

29
Q

what are secondary alcohols oxidised to produce

A

ketones

30
Q

ethan-2-ol oxidisation equation

A

CH3CH(OH)CH3 –> CH3CH3CO + H2

31
Q

potassium dichromate formula

A

K2Cr2O2

32
Q

what is potassium dichromate

A

an oxidising agent (is reduced when an alcohol oxidises)

33
Q

colour change of K2Cr2O2 when primary + secondary alcohol oxidised

A

orange - green

34
Q

colour change of K2Cr2O2 when tertiary alcohol oxidised

A

orange - orange (no colour change)

35
Q

what is used to test for aldehydes

A

benedics/fehlings solution

36
Q

describe how to use fehlings solution

A

add a few drops of solution to a gently warmed test tube containing the solution
- if aldehyde present a red precipitate will form

37
Q

what occurs in a negative result in fehlings test

A

solution stays blue (Ketones will produce a negative result)

38
Q

use of heating under reflux

A

allows reactions such as oxidation of primary alcohols all the way to formation of carboxylic acids

39
Q

use of reflux condenser

A

ensures vapours condense and return to flask for further heating- product vapours don’t escape

40
Q

role of separating funnel

A

separate two liquids of different densities

41
Q

how does a separating funnel work

A

mixture is added, liquid will separate into two layers depending on their different densities (more dense liquid will be found at the bottom)
- open tap to remove denser liquid into a different flask

42
Q

role of distillation

A

separate liquids with different boiling points

43
Q

how does distillation work

A
  • pear shaped flask heated, liquid with lower boiling point evaporates first
  • vapour rises up flask into tubes
  • condenser causes it to cool and condense into a liquid
  • is then collected in a separate flask
44
Q

how do you dry compounds

A

addition of anhydrous salts

45
Q

how does drying work

A

absorbs moisture and water present, drying and purifying the compound

46
Q

name a common anhydrous salt

A

sodium sulphate

47
Q

how do you test the purity of a substance

A

boiling point determination

48
Q

what kind of boiling point does a purer substance have

A

a closer boiling point to that of the database boiling point value

49
Q

how do you determine a substances boiling point

A
  • place into a thiele tube containing inverted capillary tube
  • substance is heated above its boiling point, it then cools and condenses back into a liquid
  • it is then drawn into the capillary tube (the temperature at which the change occurs is its boiling point)

A-level chemistry (21 decks)

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