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organic chemisrty > alcohols > Flashcards

alcohols Flashcards

1
Q

what are the two ways to make an ethanol (alcohol)

A

fermentation and hydration of ethene

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2
Q

what are the conditions for fermentation

A

room temperature, yeast and no oxygen (anaerobic respiration)

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3
Q

what are the conditions needed for the hydration of ethene

A

fractional distillation at 300°C, 70 atm and a catalyst ( conc° H₃PO₄- phosphoric acid)

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4
Q

what are the pros of fermentation

A

low energy needed, sugar is renewable, lower tech demands

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5
Q

what are the cons of fermentation

A

its a slow batch process, less efficient, the ethanol made is impure and it depletes land used to grow crops

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6
Q

what is the equation for fermentation

A

glucose → ethanol + carbon dioxide
C6H12O6 →2 CH3CH2OH + 2 CO2

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7
Q

why is fermentation done without air

A

it will oxidise the ethanol produced to ethanoic acid (vinegar)

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8
Q

what are the pros of hydration of ethene

A

its a fast reaction, the product is pure, its a continuous process

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9
Q

what are the cons of hydration of ethene

A

high tech needed which inc costs, ethene is non-renewable and lots of energy is needed which also make it more expensive

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10
Q

what is the general formula of alcohols

A

CnH2n+1OH

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11
Q

what are the boiling points of alcohol

A

they are relatively low, due to their ability to form hydrogen bonds between alcohol molecules

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12
Q

explain the trend in solubility of alcohols

A

the smaller the alcohol, the more soluble thy are because they can form hydrogen bonds to water.
The longer the chain the less soluble the alcohol

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13
Q

what are the three types of alcohols

A

primary, secondary and tertiary

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14
Q

what is the bond angle of an alcohol

A

H-C-H bond and C-C-O bond are 109.5° (tetrahedral, there are 4 BP), whereas the H-O-C bond is 104.5° (bent, there are 2 BP and 2LP)

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15
Q

what is the reaction for the combustion of alcohols

A

CH3CH2OH + 3O2 → 2CO2 + 3H2O, it reacts with a clean flame

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16
Q

what is the reaction of alcohols with sodium

A

2CH3CH2OH + 2Na → 2CH3CH2O-Na+ + H2, can be used as a test for alcohols

17
Q

what are the observations when alcohol reacts with sodium

A

effervescence (bubbles), mixture gets hot (endothermic), sodium dissolves and a white solid is produced

18
Q

what are the conditions of oxidation of alcohols

A

mild (gentle heating,)

19
Q

what is formed when primary alcohols are oxidised under mild conditions

A

they form aldehydes (which are volatile) and need to be distilled

20
Q

what is formed when primary alcohols are oxidised under stronger heating and excess oxidising agent

A

they form carboxylic acid

21
Q

why do aldehydes need to be distilled

A

to prevent further oxidation to form carboxylic acid

22
Q

how is an oxidising agent represented in a reaction

A

[O]

23
Q

what are the reagents for the partial oxidation of an alcohol

A

potassium dichromate (K2Cr2O7) an dilute sulfuric acid (H2SO4)

24
Q

what are the conditions for partial oxidation of primary alcohols

A

use a limited amount of dichromate and mild temp to gently distil out the aldehyde as it forms

25
Q

what is an observation of the partial oxidation of a primary alcohol

A

the orang dichromate ion (Cr2O7^2-) reduces to the green Cr^3+ ion

26
Q

what

A

thermometer, 2 round bottom flasks, a liebig condencer, water, ice and an electric heater

27
Q

why is an electric heater used to heat alcohol

A

as alcohols are very flammable using an open flame is very dangerous

28
Q

what is the full oxidation of primary alcohols

A

using an excess of potassium dichromate (VI) (K2Cr2O7) and dilute sulfuric acid (H2SO4), heat under reflux , this produces carboxylic acid which will need to be distilled at the end

organic chemisrty (3 decks)

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