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A-level Chemistry > Chapter 14 Alcohols > Flashcards

Chapter 14 Alcohols Flashcards

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1
Q

what is an alcohol

A

an organic compound with the OH (hydroxyl) functional group

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2
Q

what are the two ways to name an alcohol

A

-ol suffix

hydroxy- prefix

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3
Q

what is the general formula for an alcohol

A

CnH2n+1OH

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4
Q

what does polyhydric mean

A

multiple alcohol functional groups attached

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5
Q

what is the shape and bond angle of the OH functional group when bonded to a carbon

A

bent

104.5

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6
Q

what is vital when drawing the skeletal formula of an alcohol

A

the bond from the carbon must be drawn to the oxygen not the hydrogen

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7
Q

why are alcohols normally water soluble

A

> O-H is polar due to big difference in electronegativity

>this allows the H in the OH to hydrogen bond to the O in H2O

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8
Q

why do long chain alcohols not normally dissolve in water

A

since the carbon chain is so long a large part of the organic compound is hydrophobic

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9
Q

what can help increase the solubility of an alcohol

A

adding more OH groups along the chain

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10
Q

what two physical properties other than solubility do the hydrogen bonds allow the alcohol to have

A

high melting point

high boiling point

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11
Q

what two reactions can take place to form alcohols

A

hydration of alkenes

fermentation of alkenes

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12
Q

what are the three conditions required for the hydration of alkenes to form alcohols

A

> 100C temp
high pressure
acidic catalyst (phosphoric acid)

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13
Q

why do alcohols produce a blue flame when combusted

A

the OH group means that the compound is already partially oxidised so burns well

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14
Q

what does [O] represent

A

an oxidising agent

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15
Q

what are the products of an oxidation of alcohol reaction dependent on

A

whether the alcohol is primary, secondary, tertiary

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16
Q

what happens when a primary alcohol is oxidised

A

initially an aldehyde is produced as long as the solution is distilled immediately along with water. if continuously heated (refluxed) a carboxylic acid is produced

17
Q

what can you use to determine what type of organic compound the solution is

A

find the boiling point which acts as a diagnostic

aldehyde has the lowest and carboxylic acids the highest

18
Q

what is a reflux reaction

A

when you heat something more strongly with an excess of an oxidising agent

19
Q

what happens when a secondary alcohol is oxidised

A

the alcohol is refluxed to produce a ketone and water

20
Q

what happens when you try to oxidise a tertiary alcohol

A

tertiary alcohols can’t be oxidised so no reaction takes place

21
Q

what is the oxidising agent that is normally used

A 
acidified dichromate(VI) 
(Cr2O7)^2-/H+
22
Q

what observation can be made when an oxidation of an alcohol reaction takes place

A

the acidified dichromate makes the solution orange to begin then turns green when the chromium is reduced to Cr3+

23
Q

why do aldehydes have the lowest boiling point

A

it only has induced dipole-dipole intermolecular bonds

24
Q

why do alcohols have the middle boiling point

A

their OH allows for hydrogen bonding intermolecular forces

25
Q

why do carboxylic acids have the highest boiling point

A

they have both induced dipole-dipole and hydrogen bond intermolecular forces

26
Q

what are the 5 reactions that alcohos can undergo

A 
combustion
oxidation
dehydration
esterification
substitution
27
Q

what happens during a dehydration of an alcohol

A

elimination reaction where the Oh functional group and one hydrogen from one of the adjacent carbon are removed to form an alkene and water

28
Q

what are the two conditions required for a dehydration reaction

A

reflux

acid catalyst

29
Q

what happens during an esterification reaction

A

alcohol is reacted with a carboxylic acid to produce an ester and water

30
Q

how is the water molecule produced during esterification

A

the OH from the carboxylic acid and the H from the OH in the alcohol bond to form the water to allow the rest of the compound to bond

31
Q

what is the functional group of an ester

A

C-O-C=O

32
Q

what is a substitution reaction

A

reaction where one functional group is replaced by another

33
Q

give an example of one substitution reaction alcohols can undergo

A

alcohol + hydrogenhalide –> haloalkane + water

34
Q

what are the two possible conditions for a substitution reaction with a hydrogenhalide

A

reflux with hydrogenhalide
or
use sodiumhalide plus concentrated sulfuric acid

35
Q

why is sodiumhalide used more than refluxing for the substitution to form a haloalkane

A

the hydrogenhalide is produced in situ meaning that it is safer and uses less energy

A-level Chemistry (19 decks)

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