unit 3 section 3 alkenes and alcohols

Question 1

what is electrophilic addition

Answer 1

it is when the carbon double bond opens up and atoms are added to the carbon atom

Question 2

what is the test for unsaturation(alkene)

Answer 2

you add bromine water and then you shake. if the solution changes from orange to colourless then there is a double bond present in solution and is unsaturated.

Question 3

what dictates the amount of product formed in an electrophilic addition reaction

Answer 3

the amount of product form depends on what carbocation that if can form is more stable. the carbocation will be predominantly produced and is the major product whereas the other carbocations will be the minor product as they are less stable so they are less likely to be formed.

Question 4

what is the least stable carbocation and what is the most stable carbocation

Answer 4

least stable to the most stable:
primary carbocation, secondary carbocation, tertiary carbocation

Question 5

what is a polymer

Answer 5

it is a long chain formed when lots of small molecules, called monomers join together.

Question 6

what is addition polymerisation

Answer 6

it is when the double bond in an alkene opens up and allows and joins other alkenes to make a long chain.

Question 7

what are the properties of polymers

Answer 7

-they are chemically inert. this is because the bonds are non-polar.
-they have strong covalent bonds however, they have weaker inter molecular forces of attraction.

Question 8

what are plasticisers

Answer 8

they are chemicals you add to plastic to modify their properties. adding plasticisers makes the plastic more bendier.

Question 9

what is the difference between poly(chloroethene) also know as poly vinyl chloride(pvc) and normal polymers and what is its properties

Answer 9

the bonds in pvc are polar, therefore they have a permanent dipole
- pvc is a hard but brittle material

Question 10

what is a dehydration reaction

Answer 10

it is a reaction that removes water from an alcohol in order to make and alkene

Question 11

what are the two main methods to create ethanol

Answer 11

fermentation and hydrating alkenes

Question 12

explain how hydrating alkenes is done and what conditions it needs

Answer 12

hydrate the alkene using steam in the presence of a catalyst. the steam is at 300 degrees and a pressure of 60 atms, it requires a solid phosphoric(v) acid catalyst

Question 13

explain how fermentation is used to make alkenes and what are the conditions for this reaction

Answer 13

fermentation is an exothermic reaction that is carried out by yeast in anaerobic conditions. the yeast produces enzymes that convert the ethene into ethanol and carbon dioxide and the optimum temperature for the enzymes is around 30-40 degrees

Question 14

what is a biofuel

Answer 14

it is a fuel that is made from biological material that has recently died.

Question 15

what are the advantages of using biofuels

Answer 15

• they are a renewable source of energy meaning they wont run out, therefore they are sustainable
• when burning biofuels they also release carbon dioxide, however they only release the amount of CO2 the plant took as it was growing, therefore they are considered carbon neutral

Question 16

what are the disadvantages of using biofuels

Answer 16

• food vs fuel - land has to be used to grow the fuel meaning that they cannot grow food in that area and this can lead to not enough food being grown in comparison to the amount of fuel grown
• deforestation - as in some places they may need to cut down trees in order to create enough space to grow the fuel.
• fertilisers - used to increase production of fuel, however it can pollute waterways and also releases greenhouse gases.

Question 17

what is the formula for converting glucose into ethanol

Answer 17

C6H12O6 = 2C2H5OH +2CO2

Question 18

other than burning what is another way to oxidise an alcohol

Answer 18

use an oxidising agent ( acidified potassium dichromate ) K2Cr2O7.
in the reaction the K2Cr2O7 ion is reduced to Cr3+

Question 19

what are primary alcohols oxidised to

Answer 19

aldehydes (heat gently, with potassium dichromate & sulfuric acid in a distillation apparatus)- then to - carboxylic acid(heat under reflux with excess potassium dichromate)

Question 20

what are secondary alcohols oxidised to

Answer 20

ketones

Question 21

what are tertiary alcohols oxidised to

Answer 21

they cannot be oxidised

Question 22

what does the notation [o]

Answer 22

it means oxidising agent

Question 23

what does heating under reflux mean

Answer 23

means you can increase the temperature of the organic reaction to boiling without loosing any volatile solvents, reactants or products.

Question 24

what it the test for aldehydes and ketones

Answer 24

-aldehydes-fehlings & benedict solution are deep blue Cu2+ complexes of copper. they turn into a brick red precipitate(Cu2O) when heated with an aldehyde and stay blue with ketones.

-ketones-tollens reagent- silver ammonia reagent- it is reduced to silver when warmed with an aldehyde, but not with ketones. Produces a silver coat on the inside of apparatus and forms a silver mirror.