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chemistry: organic chemistry 1 > alcohols > Flashcards

alcohols Flashcards

(95 cards)

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1
Q

what is the functional group of an alcohol?

A

hydroxyl group -OH

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2
Q

what is the general formula of an alcohol?

A

CnH2n+1OH

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3
Q

what are rules for naming alcohols? (3)

A

● more than 1 -OH - keep e on name

● one -OH - remove e

● functional group has highest priority so lowest number

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4
Q

what is the bond angle of alcohols?

A

C-O-H angle - 105 degrees

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5
Q

why is the bond angle of alcohol different than expected? (2)

A

● 109.5 angle of a tetrahedron is squeezed down by presence of lone pairs

● the two lone pairs on the O repel each other more than the pairs of electrons in a covalent bond

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6
Q

what type of intermolecular forces do alcohols have? (2)

A

● hydrogen bonding

● due to the electronegativity difference in the OH bond

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7
Q

how do alcohols boiling and melting point compare to hydrocarbons of similar chain lengths? (2)

A

● higher

● hydrogen bonding is stronger than VdWs

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8
Q

are alcohols soluble in water? (2)

A

● soluble when short chain - hydrogen bonds form between the -OH groups and water molecules - water is a polar molecule and shorter chain alcohols are polar (polar solvents dissolve polar molecules - ‘like dissolves like’)

● insoluble when long chain - non polar hydrocarbon chain dominates the polar alcohol

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9
Q

what makes an alcohol primary?

A

C bonded to OH is only bonded to one other C atom

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10
Q

what makes an alcohol secondary?

A

C bonded to OH is bonded to two other C atoms

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11
Q

what makes an alcohol tertiary?

A

C bonded to OH is bonded to three other C atoms

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12
Q

what are primary alcohols oxidised to? (2)

A

● aldehydes

● further oxidised to carboxylic acid

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13
Q

what are the conditions for the further oxidation of primary alcohol into carboxylic acids? (2)

A

● oxidisation agent (acidified potassium dichromate) in excess

● under reflux

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14
Q

what are secondary alcohols oxidised to? (3)

A

● ketones

● + H2O

● can’t oxidise any further

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15
Q

what are the conditions for the oxidisation of a secondary alcohol?

A

● under reflux

● oxidising agent (acidified potassium dichromate)

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16
Q

what are tertiary alcohols oxidised to?

A

aren’t oxidised by acidified sodium or potassium dichromate (VI) solution

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17
Q

why can’t a tertiary alcohol be oxidised? (2)

A

● need to be able to remove 2 particular hydrogen atoms

● in order to set up the C=O bond

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18
Q

where are aldehydes found?

A

on the outside (R-CHO) (carbonyl group C=O at the end of chain)

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19
Q

what is the functional group of an aldehyde?

A

carbonyl group -C=O

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20
Q

what is the suffix of an aldehyde?

A

-al

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21
Q

where are ketones found?

A

in the middle of the carbon chain (R-COR’) (carbonyl group C=O within the carbon chain)

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22
Q

what is the functional ground of a ketone?

A

carbonyl group -C=O

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23
Q

what is the suffix of a ketone?

A

-one

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24
Q

what is the oxidising agent used to oxidise primary and secondary alcohols?

A

acidified potassium dichromate

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25
how do you distinguish between primary / secondary and tertiary alcohols? (3)
● acidified potassium dichromate ● primary and secondary: orange solution is reduced to a green solution ● tertiary: remain orange solution (can't be oxidised by acidified potassium dichromate)
26
what is the formula for the oxidation of primary alcohols?
primary alcohol (ethanol) --[O]--> (partial oxidation) aldehyde (ethanal) --[O in excess]-- > (full oxidation) carboxylic acid (ethanoic acid)
27
what are the conditions of the partial oxidation of primary alcohols? (3)
● excess alcohol (prevents secondary oxidation) ● NO reflux ● distill aldehyde straight away
28
what is reflux?
continous boiling and condensing of a reaction mixture
29
draw a diagram of reflux (2)
● flask with condenser vertically above it ● flask and condesner labelled
30
what are the two ways ethanol can be made? (2)
● from crude oil ● fermentation
31
how can ethanol be made from crude oil? (2)
● hydration of ethene ● via electrophilic addition
32
what are the reagents of the hydration of ethene? (3)
● alkene ● phosphoric acid catalyst ● steam
33
what are the conditions of the hydration of ethene? (2)
● 300 degrees celsius ● 60 atm
34
draw out the mechanism for the hydration of ethene
‎
35
what is the formula for the hydration of ethene?
C2H4 (g) + H2O(g) ⇌ C2H5OH (g)
36
what are the raw materials used for the hydration of ethene? is it renewable?
ethene from crude oil (non-renewable)
37
what are the waste products in the hydration of ethene?
none
38
what is the process and costs of the hydration of ethene?
● continuous process ● so expensive equipment needed ● but low labour costs
39
what is the rate of the hydration of ethene?
very fast
40
what is quality of products in the hydration of ethene like?
pure
41
what are the environmental issues with the hydration of ethene? (2)
● ethene comes from crude oil ● so it is not sustainable
42
how can ethanol be made by fermentation?
plant carbohydrates are broken down and fermented by enzymes (yeast) - ethanol
43
what are the conditions needed to make ethanol by fermentation? (2)
● 30 - 40 degrees celsius ● yeast in anaerobic conditions
44
what is the equation for fermentation?
C6H12O6 (aq) -> 2C2H5OH (aq) + 2CO2 (g)
45
what are the raw materials used for fermentation? is it renewable?
sugar (renewable)
46
what are the waste products of fermentation?
CO2 (carbon dioxide)
47
what is the process and costs of fermentation? (3)
● batch process ● so cheap equipment ● but high labour costs
48
what is the rate of fermentation?
very slow
49
what is the quality of products in fermentation like? (2)
● very impure ● yeast (fractional distillation required)
50
what are the environmental issues with fermentation? (2)
● sugar is renewable ● but a lot of land is needed to grow sugar
51
what is a bio-fuel?
a fuel produced from renewable biological sources
52
define carbon neutral
an activity that has no net annual carbon (greenhouse gas) emissions to the atmosphere
53
is ethanol a carbon neutral biofuel? (4)
● during photosynthesis, plants use CO2 to produce glucose 6CO2 + 6H2O -> C6H12O6 + 6O2 ● in fermentation, glucose is converted into ethanol C6H12O6 -> 2C2H5OH + 2CO2 ● when ethanol is burned, CO2 and H2O are produced C2H5OH + 3O2 -> 2CO2 + 3H2O ● there are 6 molecules of CO2 at the start and 6 molecules of CO2 were made ● overall no net annual carbon emissions
54
why would it probably not be entirely carbon neutral to use ethanol?
* fossil fuels burnt to transport ethanol across country * which releases CO2 into the atmosphere (a greenhouse gas)
55
write the equation for the combustion of ethanol
C2H5OH (l) + 3O2 (g) -> 3CO2 (g) + 3H2O (g)
56
in the future, how might most ethene be made? why is it not made like this at the moment? (2)
● dehydrate ethanol made by fermentation -> ethene ● not economical at the moment
57
what mechanism is the dehydration of an alcohol?
elimination
58
draw the mechanism for the dehydration of an alcohol
‎
59
which group leaves the parent molecule in the case of the dehydration of an alcohol? (2)
● OH and a H ● to form water (H2O)
60
can all alcohols be dehydrated? (2)
● no ● can't be dehydrated if there is not hydrogen atom on the carbon adjacent to the OH group
61
what are the reagents of the dehydration of an alcohol? (2)
● excess hot sulfuric acid (or conc phosphoric acid) ● at 170 degrees
62
what are the conditions of the dehydration of an alcohol? (2)
● under reflux ● 170 degrees
63
what are the products of the dehydration of an alcohol? (2)
● alkene ● water
64
why is H2SO4 used in the dehydration of an alcohol? (2)
● strong oxidising agent ● as reaction produces a lot of unwanted products
65
what else can be used to dehydrate an alcohol? (2)
● by passing vapours over heated aluminium oxide ● at 350 degrees celsius
66
what is the formula for methanol production?
CO (g) + 2H2 (g) ⇌ CH3OH (g)
67
what are the conditions of methanol production? (2)
● 220 degrees celsius ● 100 atm
68
what is the catalyst used in methanol production?
a combo of copper, zinc oxide and aluminium
69
what are the uses of methanol? (3)
● fuel mixtures ● chemical feedstock ● oxidised to ethanal - glues, paints, plastics and explosives
70
what are both fehling's solution and tollen's reagent?
gentle oxidising agents
71
what does tollen's reagent give a positive test result for? (what does it oxidise?)
aldehydes (oxidises aldehydes but not ketones)
72
what is in tollen's reagent? how does this react with the substance to be tested? (2)
‎● Ag+ ions ● are reduced to Ag(s)
73
what is the result for tollen's reagent in aldehydes and ketones? (2)
● aldehydes: silver mirror forms (solid Ag) ● ketones: no visible change
74
what does fehling's solution give a positive test result for? (what does it oxidise?)
aldehydes (oxidises aldehydes but not ketones)
75
what is in fehling's? how does this react with the substance to be tested? (2)
● blue copper (II) complex ions ● reduced to Cu+ ions (brick red)
76
what condition do you need to use fehling's and tollen's solution?
heat
77
what is the result for fehling's solution in aldehydes and ketones? (2)
● ketone: remains clear blue ● aldehyde: brick red precipitate of copper (I) oxide
78
what is the result for acidified potassium dichromate in aldehydes and ketones? (2)
● ketone: stays orange ● aldehyde: green
79
why is it not the best to use acidified potassium dichromate to distinguish between chemicals?
also turns green with primary alcohols
80
what is cyclohexanol dehydrated to? (2)
● cyclohexene ● + water
81
what are the conditions of the dehydration of cyclohexanol? (2)
● phosphoric acid (H3PO4) catalyst ● under reflux
82
draw the mechanism of the dehydration of cyclohexanol
‎
83
why do we use a pear shaped flask in the dehydration of cyclohexanol practical? (2)
● aids swirling ● has a larger surface area which allows for even more heating
84
why do we use antidumping granules in the dehydration of cyclohexanol practical? (2)
● to prevent vigorous bubbling ● to prevent formation of large bubbles
85
why do we use no lid in the dehydration of cyclohexanol practical?
prevents pressure build up
86
where is water in on a condenser?
bottom
87
where is water out on a condenser?
top
88
where should the thermometer be on a condenser? why? (2)
● opening of condenser ● so you can check the temperature of the vapour you are collecting
89
what is an improvement to the dehydration of cyclohexanol practical? (2)
● ice bath should be set up where the distillate is collected ● to ensure no vapour escapes (no loss of products)
90
why do we use a separating funnel in the dehydration of cyclohexanol practical? (4)
● when layers are immiscible (don't mix) ● they form two different layers - an aqueous and organic layer ● need to know densities ● to know what layers to collect and which to discard
91
why do we use saturated sodium chloride (or sodium carbonate) in the dehydration of cyclohexanol practical?
to remove H+ from acid - neutralises acid
92
why do we use anhydrous copper chloride in the dehydration of cyclohexanol practical? (2)
● removes water ● doesn't react with cyclohexene
93
why do we keep tap of separating tunnel open in the dehydration of cyclohexanol practical?
to avoid build up of pressure
94
what is the test for unsaturation (double bond)? (2)
● potassium permanganate (KMnO4) ● purple -> brown sludge
95
draw a diagram for fractional distillation
● attempt to draw apparatus ● suitable drawing of distillation apparatus with condenser attached to side of distillation head

chemistry: organic chemistry 1 (8 decks)

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