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chemistry ~ organic chemistry (3.3) > alcohols > Flashcards

alcohols Flashcards

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1
Q

what general uses do alcohols have

A

scientific
medicinal
industrial

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2
Q

what are two ways alcohols can be produced

A

hydration or alkenes eg ethene in the presence of an acid catalyst

ethanol can be produced by fermentation of glucose

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3
Q

describe the process of hydration of alkenes

A

crude oil separated to get ethene

in aq phosphoric (H3PO4) acid

  1. H+ ion attacks double bond
  2. forms carbocation
  3. water molecule attaches to +ve C in the molecule
  4. bond between O and one of the Hs in the added water molecule gles to completely positive O
  5. forms alcohol and H+ ion. therefore acid is a catalyst
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4
Q

adv/disad of hydration (3/3)

A

ADV
faster
purer product
continuous process so cheaper manpower

DISADV
expensive tech needed
ethene is non renewable
high energy costs for pumping to produce high pressure

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5
Q

conditions for hydration of ethene

A

300°C
60 ATM
solid / conc p(v) acid

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6
Q

describe process of fermentation to produce ethanol

conditions

A

yeast anaerobically respire to form ethanol and CO2 from water and glucose

yeast
no air
temp between 30 and 40°C

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7
Q

explain the conditions of fermentation

A

no air
further reactions could occur eg ethanol oxidised to e.acid

temp
at lower temps reaction is too slow. at higher, enzymes denature and yeast die so reaction slows/stops

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8
Q

adv/disadv of fermentation (2/3)

A

ADV
1. renewable resource (sugar)
2. uses low level tech (cheap)

DISADV
1. batch process is slow and gives high production costs
2. ethanol made is impure, have to do f. distillation after
3. depletes land use for food growth

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9
Q

ethanol is can be used as a biofuel. what’s a biofuel

A

fuel produced over short time span from biomass which can be produced from plants or domestic biowaste

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10
Q

what’s carbon neutrality

A

an activity that has no net annual carbon emissions to the atmosphere

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11
Q

Ethan produced from fermentation is a biofuel. why can it be argued that the use of it is carbon neutral?

A

CO2 given off when it is
- made as a product of resp in yeast and
- burnt
is taken in during ptts to make the glucose to use in the fermentation chamber

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12
Q

equations to show the carbon neutrality of combustion of ethanol

A

forming of glucose (ptts)
6CO2 + 6H2O -> glucose + 6O2

fermentation to produce ethanol
glucose -> 2CH3CH2OH + 2CO2

combustion
2 ethanol+ 6O2 -> 4CO2 + 6H2O

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13
Q

why is it not carbon neutral

A

energy needed to irrigate the plants

so f distillation of ethanol from reaction mixture

processing the fuel

transport

fermentation, the energy for processing, transportation, even the fertilizers used to grow plants

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14
Q

what is K2Cr2O7

A

an oxidising agent

Cr2O7 has a 2- charge btw

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15
Q

partial oxidation of primary alcohols
- reagents
- product
- conditions

A

potassium dichromate and dilute sulfuric acid

forms an aldehyde and water

heat and distill off product immediately (by having heat be above aldehyde BP)

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16
Q

partial oxidation of primary alcohols: practical set up and observation

A

dichromate ion makes reaction mixture orange initially then gets rescued to Cr3+ ion which is green

look at set up and test yourself to draw it

17
Q

full oxidation of primary alcohols:
reagent
product
conditions

A

potassium dichromate and sulfuric acid

c acid and water

heat under reflux

in this one the aldehyde is further oxidised from partial. so in eq do 2[O]

18
Q

full oxidation of primary alcohols: practical set and observation

A

look at set up

same observation

19
Q

oxidation of secondary alcohols
reagent
product
conditions

A

potassium dichromate and sulfuric acid

ketone and water

heat under reflux

20
Q

why are tertiary alcohols not easily oxidised

A

dk ibr

21
Q

the method used to oxidise a primary alcohol determines what

explain

A

what product, aldehyde or c acid is obtained

if distilling off product, aldehyde

if under reflux, c acid

22
Q

how can we distinguish between aldehyde or ketones (2)

why would we want to

A

tollens reagent
fehlings solution

you can know if you’ve got a primary or secondary alcohol by doing the distillation and the reflux for both unknowns

then doing the test for each product you get

the unknown that is positive for aldehyde must have been a primary alcohol

the unknown that isn’t must have produced a ketone so its a secondary alcohol

23
Q

outline process of tollens reagent

( a reaction / test of aldehydes )

A

tollens is a mixture of aq ammonia and silver nitrate
it forms [Ah(NH3)2]+ complex ions

heat gently

aldehydes only are oxidised into a c acid. the silver ions are reduced to silver atoms. this forms a silver mirror coating the inside of the rest tube

aldehyde + 2Ag+ + water -> c acid + 2Ag + 2H+

24
Q

outline process of fehlings

( test / reaction of aldehydes)

A

fehlings is Cu2+ ions
when heated gently it oxidises aldehydes to x acid. the ions are reduced to Cu2O which is a red precipitation

ketone + 2Cu2+ + 2water -> c acid + Cu2O + 4H+

25
Q

test for carboxylic acid

A

sodium carbonate
or sodium hydrogencarbonate

fizzing

26
Q

what is the dehydration of alcohols and what is the product

A

for alcohols that have a H on the C next to the C-OH, they can be hydrated to form alkenes and water

this is an elimination reaction

27
Q

conditions of dehydration of alcohols

A

hot conced H2SO4

180°C

28
Q

process of dehydration

A

H+ attracted to lone pair on oxygen
joins
oxygen is positive

H on the C next to the C-OH, that C-H goes to the C-C bonds

bond between C-O goes to O

forms alkenes, water + H+

29
Q

what are these alkenes produced used for maybes

A

addition polymerisation without using monomers derived from crude oil

30
Q

there are questions which ask you to determine the product based around all these alcohol reactions

how go about ?

A
  1. identify whether it’s oxidation or dehydration by examining the conditions
    - hot conced acid, high temp -> dehydration
    - H2SO4, p.dichromate, distill / reflux -> oxidation
  2. determine class of alcohol
  3. If oxidation, product depends on conditions and class
    - 1° gets ald / c acid + water , depending on distill or reflux
    - 2° gets ketone and water
    - 3° no reaction
  4. If elimination, can elimination occur? (H on C blah blah)
  5. If yes then alkene and water, if no then no reaction

chemistry ~ organic chemistry (3.3) (9 decks)

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