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Georges chem > alcohols chp 14 > Flashcards

alcohols chp 14 Flashcards

1
Q

what gives alcohols there physcial and chemical properties

A

The Hydroxyl group (-OH)

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2
Q

what are some difference between the characteristic of alcohols and alkanes

A
  • they have higher melting/boiling points
  • they have greater water solubility (than there corresponding alkanes)

  • The differences become smaller as chain length increases
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3
Q

Descibe and explain what effect the polarity of alkanes has on its characteristics

A
  • non-polar due to electronegativity similarity bonding elements
  • intermolecular forces between non-polar molecules are very weak London forces leads, to low melting and boiling points
  • insoluble in polar solvents
  • soluble in non-polar solvents
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4
Q

Descibe and explain what effect the polarity of alcohols has on its characteristics

A
  • alcohols are polar due to presence of OH group making them soluble in some polar solvents
  • higher melting and boiling points than respective alkanes
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5
Q

what does the trend in boiling points between alcohols and alkanes look like

A
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6
Q

define Volatility

A

how easily a substance will vaporize

volatile liquids have a low boiling point

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7
Q

what alcohols if any are soulble in water and explain why they are

A

alcohols such as methanol and ethanol are completely soluble in water as hydrogen bonds form between the polar OH groups of the alcohols and the water molecules

Longer chain are less soluble due to the effect of the OH group becomeing less prevelant with increasing chain length

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8
Q

what is a primary alcohol

A
  • OH group in alcohol attached to carbon attached to 2 hydrogens and a single carbon
  • 3 hydrogens in methanol case
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9
Q

what is a secondary alcohol

A

The alcohol is OH group is attached to a carbon atom that is attached to 1 hydrogen atom and 2 alkyl groups

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10
Q

what is a tertiary alcohol

A

The OH group is attached to a carbon atom that is attached to no hydrogen atoms and 3 alkyl groups

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11
Q

can alcohols be oxidised, if so which alcohols

A
  • Primary and secondary alcohols can be oxidised (using [o], acidfied potassium dichromate(VI) K2Cr2O7/H+)
  • Tertiary alcohols cannot be oxidised
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12
Q

what colour change occurs when alcohols are oxidised

A

orange to green

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13
Q

what are primary alcohols oxidised into

A

-Primary alcohols can be oxidised to either aldehydes or carboxylic acid
-The product of the oxidation depends on the reaction conditions used (aldehydes are themselves oxidised to carboxylic acids)

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14
Q

how do you obtain aldehydes from alcohols

A
  • distill primary alcohols with acidified potassium dichromate
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15
Q
  • how do you obtain a carboxylic acid from an alcohol
  • write reaction
A
  • reflux primary alcohol with excess acidified potassium dichromate (VI) (ensures all alcohol is oxidised)
  • reflux ensures any aldehyde formed undergoes oxidation to form carboxylic acid.
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16
Q

what are secondary alcohols oxidised into

A

They are oxidised into ketones (it is not possible to further oxidise ketones using acidified dichromate ions)

17
Q

what is the process to obtain a ketone from a secondary alcohol

A

you heat the secondary alcohol under reflux with excess acidified dichromate ions

-you heat under reflux to ensure that all alcohol has been reacted - you add excess to ensure that the all the alcohol is allowed to react -There will be a colour change from orange to green

18
Q

what is a dehydration reaction

A

dehydration is any reaction in which a water molecule is removed from the starting material

19
Q

whats the process to dehydrate an alcohol

A
  • heat alcohol under reflux in presence of acid catalyst conc H2SO4, or conc (phosphoric acid) H3PO4.
  • produces alkene
20
Q

what are the products of a dehydration reaction with an alcohol

A

water + alkene

21
Q

what type of reaction is a dehydration reaction

A

An elimination reaction

22
Q

what is a substitution reaction

A

an atom, ion, or group of atoms or ions in a molecule is replaced by another atom, ion, or group

23
Q

What is an example of a substitution reaction that alcohols can undergo

A

alcohols react with hydrogen halides to form haloalkanes

24
Q

what is the process to produce a haloalkane from an alcohol

A
  • alcohol is heated under reflux with sulphuric acid and a sodium halide,
  • ^hydrogen halide is formed which reacts with alcohol to produce a haloalkane, salt and water
25
Q

what does the hydrogen halide reaction with the alcohol chemical equation look like

A

Georges chem (29 decks)

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