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LC Chemistry > organic synthesis > Flashcards

organic synthesis Flashcards

1
Q

organic synthesis

A

process of making organic compounds from simpler starting materials

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2
Q

what do we call the compound you want to make

A

target molecule

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3
Q

what are intermediate compounds

A

compounds that you make on the way to the target molecule

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4
Q

what is the purpose of a mechanism

A

they show how electrons rearrange when a chemical reaction happens

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5
Q

is breaking bonds endo or exothermic

A

endo

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6
Q

when bonds are formed is that endo or exothermic

A

exo

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7
Q

how to identify a substitution reaction

A

start with 2 molecules end up with 2

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8
Q

how to identify a addition reaction

A

start with 2 molecules end up with one

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9
Q

how to identify an elimination reaction

A

start with 1 molecule end up with 2 molecules

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10
Q

how to identify a redox reaction

A

is something gaining or loosing oxygen/ forming double bonds to Oxygen

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11
Q

substitution reaction

A

a chemical reaction in which an atom or group of atoms in a molecule is replaced by another atom or group of atoms

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12
Q

what are the 2 substitution reactions

A

halogenation of alkanes
esterification

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13
Q

uses of halogenated alkanes

A

they do not support combustion so are used as fire extingushers

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14
Q

free radical

A

an atom/ molecule/ group of atoms that contain s unpaired electron

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15
Q

how are free radicals presented

A

a dot

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16
Q

how reactive are free radicals

A

extremely reactive as they do not have a stable outer octet

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17
Q

homolytic fission

A

each atom joined by the bond keeps one of the 2 electrons in the bond

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18
Q

write the mechanism for the monochlorination of methane

A

initiation
propagation
propagation (chain reaction step)
termination

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19
Q

evidence for free radical substitution

A

takes place under UV light- suggests that a free radical mechanism occurs where Cl2 is split into 2 chlorine free radicals

for every photon of light absorbed, thousands of chloromethane molecules form- evidence for chain reaction

small amounts of ethane formed- methyl free radicals combine to form ethane

adding a source of free radicals eg tetraethyllead speeds up the rate of reaction- this decomposes to produce methyl radicals which then increase the rate of the reaction

if an inhibitor is added the rate of the reaction slows down-the inhibitor combines with free radicals to stop the chain reaction from occuring

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20
Q

what is hydrolysis?

A

the reverse reaction of esterification
ie
ester + water —–> alcohol and carboxylic acid

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21
Q

saponification

A

base catalysed hydrolysis of esters with a carboxylate salt is formed

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22
Q

describe hydrolysis

A

a chemical reaction where something reacts with water
the ester reacts with OH- and H+ and the ester breaks apart
a base is a very effective reactant to hydrolyse an ester. the most commonly used us sodium hydroxide

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23
Q

addition reaction

A

a reaction where 2 or more molecules react together to form a single product

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24
Q

use of 1,2-dichloroethane

A

used to make PVC

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25
Q

use of 1,2-dibromoethane

A

used to fumigate logs for termites and beetles

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26
Q

use of ethanol

A

solvent

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27
Q

use of chloroethane

A

used to test for a dead tooth is placed on a tooth and causes cooling. if you cannot feel the cooling the tooth is dead

28
Q

write the mechanism for an addition reaction

A

polarisation
heterolytic fission
carbonium ion formation
ionic addition

29
Q

evidence for an addition mechanism

A

a mixture of products is formed when ethene reacts with Br2 in water with sodium chloride dissolved in water 3 possible products can be formed:
1,2-dibromoethane
1-bromo-2-chloroethane
2-bromoethanol

30
Q

how to identify an addition reaction

A

starting material is unsaturated

31
Q

what does poly unsaturated mean

A

more than one c double bond c

32
Q

which oils are polyunsaturated

A

sunflower oil, palm oil, corn oil

33
Q

which fats are saturated

A

animal fats

34
Q

which fats are unsaturated

A

vegetable fats (better for your health)

35
Q

what is polymerisation

A

a type of addition reaction and is how some polymers are formed. 2 c double bond c add together in addition polymerisation

36
Q

what is the unit that polymers are mode up of?

A

monomers

37
Q

which fraction is used to manufacture a large number of polymers

A

crude oil

38
Q

what is poly ethene

A

a synthetic man made polymer formed when many ethene monomers join together by addition polymerisation

39
Q

what does PVC stand for

A

poly(vinyl chloride)

40
Q

uses of polymers

A

plastic, nylon

41
Q

what are monomers

A

building blocks of the polymer
they are the starting material that you use to form the polymer. monomers for addition reactions MUST have a double bond

42
Q

polymer

A

a polymer is a long chain molecule made by joining together many small repeating units/ molecules called monomers

43
Q

repeating unit

A

part of the polymer that repeats and completes the polymer chain except for the end groups

44
Q

how do you draw the repeating unit of a polymer

A

draw 3 monomers side by side
break the double bond and draw a bond linking each monomer together and the blank bonds on the end carbons
place brackets around the whole thing

45
Q

draw the monomer of poly(x)

A

draw the structure of x

46
Q

what is another name for vinylchloride

A

chloroethene

47
Q

how do you revert back from the repeating unit to the monomer

A

remove the bracket
put a double bond between the C atoms
remove the end bonds

48
Q

draw the synthesis of PVC

A
49
Q

elimination reaction

A

a reaction in which a small molecule is removed from a larger molecule and a double bond is formed in the larger molecule

50
Q

what is a dehydration reaction

A

if the elimination reaction removes water

51
Q

what are some oxidising agents

A

acidified sodium dichromate
acidified potassium permanganate

52
Q

what colour change is observed with acidified sodium dichromate

A

orange (Cr+6) to green (Cr+3)

53
Q

what colour change is observed with acidified potassium permanganate

A

purple Mn+7 to colourless Mn+2

54
Q

what is the reducing agent

A

hydrogen gas over a Ni catalyst

55
Q

what is used to oxidise ethanal is the liver

A

ethanol

56
Q

explain the oxidation of a primary alcohol to an aldehyde then a carboxylic acid

A

using an oxidising agent in excess, the primary alcohol will be oxidised into an aldehyde and then further into a carboxylic acid. this can be reversed using H2/Ni

57
Q

explain the oxidation of a secondary alcohol to a ketone

A

if an oxidising agent reacts with a seondary alcohol a ketone is formed. acidified potassium permanganate is a weak oxidising agents and it is not strong enough to oxidise a ketone further so there is only one oxidation product

58
Q

which functional groups are acidic

A

alcohols and carboxylic acids

59
Q

are alcohols strong or weak acids

A

weak acids so they do not react with bases

60
Q

under what circumstances do alcohols react as acids

A

in the presence of very reactive metals such as sodium

61
Q

what is formed when carboxylic acids react with metals

A

hydrogen gas

62
Q

what is formed when carboxylic acids react with metal carbonates

A

salt water and carbon dioxide

63
Q

what is formed when carboxylic acids react with alcohols

A

esters

64
Q

why do carboxylic acids behave as acids

A

the inductive effect
stability of the carboxylate group

65
Q

what is the inductive effect

A

where the carbonyl group pulls electron density from the H in the OH group which makes it easier to ionise the OH group to form -COO- and H+

66
Q

what is the stability of the carboxylate ion

A

if the carboxylic acid group looses a proton it forms a negative ion called a carboxylate ion
the negative charge on the carboxylate anion is actually shared/ spread across the 3 atoms. this is called a resonance hybrid and provides extra stability to the ion

LC Chemistry (22 decks)

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