alcohols

Question 1

what is the suffix of all alcohols ?

Answer 1

-ol

Question 2

what is the general formula of alcohols ?

Answer 2

CnH2n + 1 OH

Question 3

what is the functional group of alcohols ?

Answer 3

OH

Question 4

what is the prefix/ name given to the functional group of alcohols if they are not the most important group in the molecule ?

Answer 4

hydroxy

Question 5

what is it called when there are 2 alcohol functional groups in the molecule ?

Answer 5

diol

Question 6

what is the additional subclass of all alcohols ?

Answer 6

primary alcohols
secondary alcohols
tertiary alcohols

Question 7

how do you know if an alcohol is a primary , secondary or tertairy alcohol ?

Answer 7

you look at the carbon that is attached to the functional group and count how many carbons are attached to that specific carbon

Question 8

what are the features of the bonds in alcohols ?

Answer 8

• dipole dipole bonding
  oxygen is more electronegative than hydrogen
• lone pair of electrons on oxygen
  so hydrogen bonds can form between lone pair and electron deficient hydrogen in a neighbouring alcohol

Question 9

what is the melting and boiling point of alcohols ?

Answer 9

hydrogen bonds between molecules means alcohols have a higher melting point than alkenes

Question 10

what is meant by solubility ?

Answer 10

the ability to dissolve in water

Question 11

describe the solubility of alcohols and explain why is that the case ?

Answer 11

alcohols are soluble in water
- because they form hydrogen bonds with water
-but the longer an alcohol gets, the less soluble it becomes

Question 12

what is the bond angle between the hydrogen bond and the O-H bond ?

Answer 12

always 180 degrees

Question 13

which point are alcohols considered to be insoluble ?

Answer 13

from octan-1-ol
there is a gradual change before that

Question 14

what is considered to be he most important alcohol ?

Answer 14

ethanol

Question 15

what are the 2 different ways of producing ethanol ?

Answer 15

• hydration of ethene
• fermentation

Question 16

what are the benefits of producing ethanol from crude oil and ethene ?

Answer 16

• very fast method
• the products of hydration are already pure
• the method is a continuous process

Question 17

what are the disadvantages of fermentation ?

Answer 17

-a very slow process
- products need to be distilled as it isn’t 100% pure
- batch process

Question 18

state the overall equation for the hydration of ethene to produce ethanol ?

Answer 18

CH2 = CH2 + H2O —> C2H5OH

Question 19

what reagent/ condition is essential for the hydration of ethene ?

Answer 19

a phosophuric acid catalyst must be added ( H3PO4)

Question 20

show the hydration of ethene mechanism

Answer 20

picture is on your phone

Question 21

how do you know that here was a catalyst present at the end of the hydration of ethene ?

Answer 21

because you are left with a H+ ion that was also there at the beginning
- this means it can be reused

Question 22

state the overall equation for fermentation ?

Answer 22

C6H12O6 —->2 C2H5OH + 2 CO2

Question 23

what are the reagents / conditions needed for fermentation ?

Answer 23

• yeast
• 35 degrees as a compromise because a high temp would speed up the reaction but also cause the enzymes to denature
• anaerobic conditions ( no oxygen )
• distillation of product to separate ethanol from the water as ethanol has a lower boiling point than water

Question 24

what is happening in fermentation ?

Answer 24

it is the anaerobic respiration of the yeast

Question 25

what would occur if oxygen was present during fermentation ?

Answer 25

ethanol would be oxidised and it would produce ethanoic acid

Question 26

what is the boiling point of ethanol and what is the boiling point of water ?

Answer 26

ethanol = 78 degrees water = 100 degrees

Question 27

what does it mean if something is carbon neutral ?

Answer 27

carbon dioxide taken in during the process = the carbon dioxide released during a process

Question 28

what is the process that takes in carbon dioxide needed for the process ?

Answer 28

photosynthesis

Question 29

is the process y which carbon dioxide is released ?

Answer 29

fermentation + combustion of the alcohol produced

Question 30

what is ethanol classified as ?

Answer 30

ethanol is a biofuel

Question 31

in what reactions is ethanol most commonly used in ?

Answer 31

used in combustion reactions

Question 32

what is the equation for the combustion of ethanol ?

Answer 32

C2H5OH + 6O2 ---> 4CO2 + 6H2O

Question 33

what happens to the CO2 in all of the 3 processes ?

Answer 33

CO2 in = CO2 out

Question 34

why is the process of fermentation not completely carbon neutral even though it seems like it ?

Answer 34

because the processes involved in between the other processes such as transporting of the crops from one place to another releases co2 that is not considered in the equations

Question 35

what are the 2 main alcohol reactions ?

Answer 35

- elimination reaction - oxidation

Question 36

what is meant by an elimination reaction ?

Answer 36

- a reaction where a small molecule leaves a parent molecule

Question 37

what do alcohols always use in elimination reactions and other reactions ?

Answer 37

they always lose water (H2O) the -OH is from the alcohol group the -H is from the Carbon adjacent to the alcohol group

Question 38

what are all elimination reactions with alcohols also known as ? and why ?

Answer 38

dehydration reactions - as we lose water

Question 39

what are the reagents and conditions for dehydration/ elimination reactions ?

Answer 39

- 600K - Aluminium oxide catalyst (Al2O3)

Question 40

what is the test to make sure that you made an alkene during elimination reactions ?

Answer 40

bromine water goes from yellow / orange to colourless

Question 41

what are the most common catalysts used in acid catalysed elimination ?

Answer 41

concentrated sulfuric acid (H2SO4) concentrated phospohoric acid (H3PO4)

Question 42

what does the dehydration / elimination of primary alcohols result in ?

Answer 42

1 alkene

Question 43

what does the dehydration of a secondary alcohol result in ?

Answer 43

2+ alkenes - due to isomeric products being made

Question 44

wat does the dehydration of a tertiary alcohol produce ?

Answer 44

results usually in mixtures

Question 45

what cannot happen to tertiary alcohols ?

Answer 45

they cannot be oxidised easily

Question 46

what is meant by oxidation ?

Answer 46

oxidation is the - gaining of oxygen - loss of hydrogen - loss of electrons

Question 47

what does the oxidation of secondary alcohols result in ?

Answer 47

the oxidise to form ketones

Question 48

what does the oxidation of primary alcohols result in ?

Answer 48

they oxidise to form aldehydes - and then they can be oxidised further into carboxyllic acids - or, under the right conditions, they can be directly oxidised to form carboxylic acids

Question 49

what is added to the distillation flask and mixture ?

Answer 49

anti bumping granules potassium dichromate dilute sulfuric acid (H2SO4)

Question 50

what is the function of anti bumping granules ?

Answer 50

ensures that the boiling is no too violent

Question 51

what is the oxidizing agent in distillation ?

Answer 51

potassium dichromate K2Cr2O7

Question 52

why does distillation work to produce the aldehyde ?

Answer 52

the strongest attraction in aldehydes is dipole-dipole whilst the alcohols have hydrogen bonding which is the strongest intermolecular force so alcohols have a higher boiling point

Question 53

what are the conditions and reagents needed for the reflux reaction directly into a carboxylic acid ?

Answer 53

- conc H2SO4 - excess K2CR2O7 - reflux

Question 54

what is the purpose of doing a reflux reaction ?

Answer 54

- it allows you to carry out a reaction at the boiling point of the chemicals without losing any reactants or products

Question 55

what do you write instead of the formula for the oxidising agent in an oxidation equation ?

Answer 55

[O]

Question 56

2 ways for testing for an aldehyde

Answer 56

- Warm , Fehling's reagent observation = red precipitate - warm Tollen's observation = silver mirror

Question 57

testing for a carboxylic acid

Answer 57

-add Na2CO3 ( sodium carbonate) solution or powder observation = effervescence (fizzing) due to CO2 being produced

Question 58

testing for primary or secondary alcohols

Answer 58

- add (acidified )potassium dichromate (K2CR2O7) and H2SO4 and warm it observation = orange to green colour change

Question 59

test for ketones

Answer 59

add Fehling's reagent or Tollen's and warm it observation = no visible change to prove it is not an aldehyde