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Chemistry Module 4 > Alcohols > Flashcards

Alcohols Flashcards

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1
Q

Describe an alcohol

A
  • saturated containing only single covalent bonds
  • have the formula CnH2n+1OH
  • have a gradation in physical properties
  • have similar chemical properties
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2
Q

How do you classified alcohols

A
  • by where there functional group is in the chain
  • primary
  • secondary
  • tertiary
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3
Q

How do you know that it is a primary alcohol

A
  • a primary alcohol has the alcohol group attached to an end of the chain
  • draw this
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4
Q

How do you know that it is a secondary alcohol

A
  • a secondary alcohol has the alcohol group attached to a carbon atom with two alkyl chains and one hydrogen atom
  • draw this
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5
Q

How do you know that it is a tertiary alcohol

A
  • a tertiary alcohol has an alcohol group attached to a carbon atom with 3 alkyl chains attached
  • draw this
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6
Q

Describe the trends of boiling points of alcohols

A

the boiling points of alcohols increase as the chain length increases, molecules get longer therefore there are more surface area contacts and there a stronger induced dipole-dipole intermolecular forces, therefore more energy is being needed to overcome the attractive forces and therefore a higher boiling points

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7
Q

Why are there boiling points of alcohols larger than there corresponding alkanes

A
  • there are hydrogen bonds between alcohol molecules, these are the strongest type of intermolecular forces of attraction therefore a greater amount of energy is needed to overcome the force of the hydrogen bond therefore the boiling point of the alcohol is higher than that of the alkane
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8
Q

Describe the evaporation trends of alcohols

A
  • volatility increases as the boiling point decreases, therefore shorter chains are more volatile then long chains
  • alcohols have hydrogen bonds which make it less volatile then corresponding alkanes
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9
Q

Describe the solubility trends of alcohols

A
  • water molecules are polar and so is the alcohol functional group therefore the molecules form hydrogen bonds with the molecules so they are soluble, this is described as miscibility
  • as alcohol length increases the solubility of alcohol decreases
  • the aliphatic chain cannot form hydrogen bonds and instead becomes part of the larger molecule
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10
Q

what are the products when alcohols are burnt

A

carbon dioxide and water

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11
Q

why is alcohol combusted

A
  • alcohol can be used as fuels as they release there stored chemical energy in the form of thermal energy
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12
Q

What happens when you oxidise a tertiary alcohol

A

there is no reaction and potassium dichromate remains orange

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13
Q

What happens when a primary alcohol is oxidised, not under reflux

A

Aldehyde is produced and water

  • heated with concentrated sulphuric acid, and potassium or sodium dichromate then distilled immediately
  • the alcohol groups loses its hydrogen atoms and is partially oxidised
  • colour change orange to green
  • write the reaction for propan-1-ol
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14
Q

What happens when a primary alcohol is oxidised under reflux

A

Carboxylic acid is produced

  • strongly heated with concentrated sulphuric acid and potassium or sodium dichromate
  • full oxidation occurs
  • write the reaction for propan-1-ol
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15
Q

What happens when secondary alcohol is heated under reflux

A

Ketone is produced

  • strongly heated with concentrated sulphuric acid and potassium or sodium dichromate
  • ketone does not undergo any more reaction
  • write the reaction of butan-1-ol
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16
Q

What is esterification used for

A

to make an ester

17
Q

What do you use to make an ester

A

carboxylic acid and alcohol

18
Q

how do you make an ester

A
  • react an alcohol with carboxylic acid in the presence of acid catalyst usually sulphuric acid, 8- degrees and sweet smell noticeable this is a reversible reaction and has a slow rate
  • the O-H bond in the alcohol and the C-O bond in the carboxylic acid are broken, new bonds are made between the H and O-H to form water
  • two remaining species bond to form the ester
19
Q

Properties of ester

A
  • small-molecule esters are soluble in water and many are visible as an oily layer floating on top of the reaction mixture
20
Q

who names esters

A

IUPAC

21
Q

How do you name esters

A
  • first part is the name of the alkyl chain that was attached to the alcohol group
  • the second part is the stem of the name of the carboxylic acid with the -oate on the end
22
Q

Draw methyl ethanoate

A

DRAW IT

23
Q

What is dehydration

A
  • a chemical reaction in which water is lost from an organic compound this is an elimination reaction and it makes an alkene
24
Q

Describe dehydration

A

alcohols are heated strongly and refluxed with concentrated sulphuric acid or another strong acid and 170 degrees, the water is eliminated, the OH group from one carbon atom and the H atom on an adjacent carbon atom lost to form a water molecule, the pie bond forms between the two adjacent carbon atoms

25
Q

Draw dehydration of ethanol

A

draw it

26
Q

What is halide substitution

A
  • halide ions react with alcohols and the halide takes the place of the alcohol group to form the haloalkane
27
Q

Describe Halide substitution

A
  • react alcohol with a reagent which would be hydrogen halide like HCL or NaBr, this reacts with the sulphuric acid to make HBR
  • acid catalyst like sulphuric acid is added and the mixture warmed to increase the rate of reaction
  • however the iodide is reactant then phosphoric acid is used because the sulphuric acid oxidises iodide ions to iodine therefore it would make the yield of iodoalkane low

Chemistry Module 4 (8 decks)

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