Topic 6- Organic chemistry Flashcards
(105 cards)
1
Q
what is a displayed formula and draw an example
A
shows all the bonds and atoms in a specific formula
2
Q
what is a structural formula and draw an example
A
a formula which shows how the atoms are joined together
3
Q
what is a skeletal formula and draw an example
A
formula which shows all the bonds between the carbon atoms
4
Q
what is a molecular formula and give an example
A
shows the numbers of each atom in a specific formula , for example ; C4H10
5
Q
what is an empirical formula and give an example
A
- shows the numbers of each atom in the simplest whole number ratio
EXAMPLE : C6H12 —> C3H4
6
Q
what is the rule for naming types of molecules in different types of formulae
A
- start from the end of the longest carbon chain that gives the functional group the lowest possible number
- if no functional groups are present , start naming from the side with the end nearest to a side chain or a multiple bond
- the functional groups must be named in alphabetical order
- commas between numbers and dashes between numbers and words
7
Q
what is a homologous series
A
a group of compounds with the same functional group that have the same chemical and physical properties and react the same way
8
Q
what is a functional group
A
an atom or a group of atoms that determines how the compound reacts in a chemical reactions
9
Q
name this compound
A
3-ethyl-2-methyl pentane
• ethyl has been put first because it comes before m in the alphabet
10
Q
name this compound
A
3-methylbutan-2-ol
- this is not called 2-methylbutan-3-ol because the lowest locant number should be used for the functional group
11
Q
name this compound
A
3,3-dimethylbutan1-ol
12
Q
draw the structural formula of 3-methylbutan-1-ol
A
13
Q
what are the three main processes that converts crude oil into fuels
A
- reforming
- cracking
- fractional distillation
14
Q
what is the process of fractional distillation
A
- firstly, the crude oil is heated until it is vaporized and passed through the bottom of a fractionating column where it is very hot at the bottom and colder at the top
- as the vapour passes through the fractionating column , different fractions condense at different heights in the column depending on their boiling point
- mostly longer chained hydrocarbons condense at the bottom where it is very hot due to their high boiling temperatures
- whereas shorter chained hydrocarbons will condense towards the top where it is cool due to their lower boiling points
15
Q
why do some hydrocarbons in crude oil rise to the top without condensing
A
because some hydrocarbons have very low boiling points that the fractionating column can’t accommodate , so they stay in gaseous form
16
Q
why is the process of cracking carried out
A
- because there is an increase in demand for smaller chained hydrocarbons because they act as better fuels
- smaller chained hydrocarbons can be used to make polymers
17
Q
what is cracking
A
cracking is the process of breaking down longer chained hydrocarbons into smaller , more useful chained hydrocarbons
18
Q
what are the conditions for catalytic cracking
A
- zeolite catalyst and 450 degrees celcius and 450 atm
19
Q
why is a catalyst used in catalytic cracking
A
because a catalyst lowers activation energy by providing an alternative reaction pathway which saves energy and time and lowers costs.
20
Q
what is the product of catalytic cracking
A
alkanes
21
Q
what are the conditions for thermal cracking
A
high temperature and high pressure
22
Q
what is the product of thermal cracking
A
alkenes
23
Q
what is reforming
A
reforming is the process of breaking down straight chained alkanes into branched - chain alkanes or cyclic compounds
24
Q
why is the process of reforming carried out
A
- to reduce knocking ( fuels burn too early) in engines so that the fuels in the engine can burn much more smoothly
- to produce fuels with a higher octane number
25
give an example of reforming reactions for pentane by using skeletal formulae
26
give an example of a reforming reaction for heptane using skeletal formula
27
what is the by product of reforming reactions
H2
28
why does the polarity down the group of halogenalkanes decrease
because the number of shells increase down the group , which increases shielding which means the strength between the nucleus and the outer shell decreases
29
draw the mechanism for the nucleophile forming a bond with the electron deficient carbon atom
30
why is it better for the lone pair of electrons to approach the carbon atom from the side without the halogen
- because there will be less repulsion that is experienced between the nucleophile and the halogen that way
31
how should you draw the curly arrow when representing the nucleophile making a bond with the carbon atom in halogenalkanes
- the curly arrow must start at the lone pair of electrons and end at the electron deficient carbon atom
32
explain the steps of nucleophillic substitution for halogenalkanes
1) the nucleophile donates its lone pair of electrons to the electron deficient carbon atom to form a bond with the carbon atom
2) the bond between the carbon and halogen atom breaks and the electrons from the bond move to the halogen atom
3) the nucleophile then attaches itself to a carbon atom and a halide ion forms
33
draw an example of nucleophillic substitution for halogenalkanes
34
why is the breaking of the bond between the carbon and a halogen atom an example of heterolytic fission
because a halide ion is produced when the carbon - halogen bond breaks , which is what is produced in heterolytic fission
35
what else do scientists call the nucleophillic substitution reactions
- hydrolysis reactions
36
what are the conditions for nucleophillic substitution with hydroxide ions in haloalkanes
- heat under reflux
- ethanol
- aqueous hydroxide ions ( a hydroxide compound dissolved in water)
37
why do we need ethanol as one of the conditions in the nucleophillic substitution of halogenalkanes
- ethanol solubilises the halogenalkane so that the halogenalkane can react with the aqueous hydroxide ions
38
why do we need heat under relflux
- to increase the rate of reaction.
39
what does the rate of hydrolysis depend on in halogenalkanes
- the halogen atom
40
how do we measure the rate of hydrolysis in halogenalkanes
- by measuring the formation of halide ions in aqueous silver nitrate
41
explain how we measure the rate of hydrolysis in halogenalkanes step by step
1) take 3 test tubes and place 1cm3 of ethanol in each one
2) then , place 0.1cm3 of a haloalkane in each test tube
3) then , place all 3 test tubes in a water bath that’s heated up to 60*c
4) then , in a separate test tube , add your aqueous silver nitrate and put it in the same water bath
5) then wait 10 minutes for all of your solutions to reach the same temperature
6) place 1cm3 of aqueous silver nitrate into all 3 test tubes and start timing
42
what happens once you add your aqueous silver nitrate to your 3 test tubes containing haloalkanes?
- the water from the aqueous silver nitrate acts as a nucleophile and starts to react with the carbon atom from the halogenalkane and hydrolysis takes place
43
what is released during the hydrolysis ?
a halide ion
44
what does the halide ion and the silver
ions do
the halide ions react with the sliver ions to produce an insoluble precipitate of silver halide
45
what colour is a silver chloride precipitate
white
46
what colour is a silver bromide precipitate
- cream
47
what colour is a silver iodide precipitate
- yellow
48
what is the bond angle and name for a molecule with 2bp and 0lp , draw the shape of the molecule aswell (BeCl2)
- linear
-180 degrees
49
what is the name and bond angle of a molecule with 2 bond pairs and 0 lone pairs , draw the shape of this molecule
- linear
-180 degrees
50
write the bond angle and bond name of a molecule with 0 lone pairs 3 bond pairs ,
draw the shape of the molecule
- trigonal planar
- 120 degrees
51
write the name of the bond angle and bond name with 4 bond pairs and 0 lone pairs and
draw the shape of the molecule
- tetrahedral
- 109.5
52
write the name of the bond angle and name for a molecule with 5 bond pairs 0 lone pairs and draw the shape of the molecule
- trigonal bipyramidal
- 90 degrees and 120 degrees
53
what is the bond angle and the bond name for a molecule with 6 bond pairs and 0 lone pairs
- octahedral
- 90 or 180 degrees
54
what is the bond angle and name for a molecule with 3 bond pairs and 1 lone pair , draw the shape of the molecule
trigonal pyramidal
- 107 degrees
55
what is the bond angle and bond name of the molecule with 2 bond pairs and 2 lone pairs , draw an example
- V - shaped
- 104.5
56
what does the electron repulsion theory state
- the shape of a molecule is created due to the electron repulsion in the pairs of electrons in a bond pair or a lone pair
- atoms surround themselves around the central atom because the repulsion there is at a minimum
- lone pair - lone pair > lone pair - bond pair > bond pair - bond pair
57
name in order which silver halide precipitates will form the slowest to the fastest and explain why in terms of bonds
-AgCl will form the slowest because it has the strongest bonds
-AgBr
-AgI will form the fastest because it has the weakest bonds
58
how many stages does the reaction between haloalkanes and ammonia have
2 stages
59
what acts as the nucleophile in the reaction between haloalkanes and ammonia
the nitrogen atom
60
describe what happens during stage 1 of the reaction between the haloalkane and the nitrogen atom
- the nitrogen atom is attracted to the electron deficient carbon atom and donates its lone pair of electrons to form a covalent bond
-because carbon can form 4 bonds , it breaks the covalent bond it has between the bromine atom and both electrons move to the halogen atom to form a bromide ion
- at the end of the stage , we have a molecule with a positively charged nitrogen atom and a bromide ion
61
what type of mechanism takes place in stage 1 of the reaction between ammonia and haloalkanes
nucleophilic substitution
62
describe what happens in the second stage of the reaction between haloalkanes and ammonia and draw it
- a second molecule of ammonia removes a H+ ion from the nitrogen atom
- the covalent bond then breaks between the hydrogen and nitrogen atom and the electrons move to the nitrogen atom / ion
- this forms 1-aminopropane , which is a primary amine and it forms NH4+ which bonds with the bromine atom to form ammonium bromide
63
what is the purpose of reacting haloalkanes with ammonia
to produce primary amines
64
what are the conditions for haloalkanes and ammonia
- in a sealed tube
- warm the haloalkane with concentrated excess ammonia solution in ethanol
65
why is the reaction of haloalkanes + ammonia carried out in a sealed tube
to increase the pressure of the reaction AND prevent ammonia from escaping as a gas
66
why do we use excess ammonia in the reaction of haloalkanes + ammonia
to make it more likely that the nitrogen with the lone pair of electrons in the primary amine reacts with the ammonia instead of acting as a nucleophile and reacting with any unreacted haloalkanes
67
write the structural formula of the reaction that takes place in stage 1 of ammonia + haloalkane
CH3CH2BR + NH3 --> CH3CH2NH3 + BR-
68
what are the reagents and conditions needed for halogenalkanes and cyanide ions
- heat under reflux
- aqueous solution of potassium cyanide
- mix haloalkane with ethanol
69
what type of compound do you form when you react a haloalkane and aqueous potassium cyanide + give an example
you form a nitrile : butanitrile
70
draw the reaction between a haloalkane and cyanide ions
71
why is it called butanintrile and not propannitrile
because we name the product based on the new carbon chain NOT the old one
72
what are the two types of reactions you can carry out with hydroxide ions in haloalkanes
elimination reactions and nucleophillic substitution
73
describe the elimination reaction of the hydroxide ions and the haloalkane , use examples
halogenalkane + potassium hydroxide --> alkene +potassium bromide + water
- in this reaction , the hydroxide ions from potassium hydroxide acts as a base and the bromine and the adjacent hydrogen atom gets removed
74
why is the reaction between haloalkanes and cyanide ions useful
because it increases the length of the carbon chain
75
what are the reagents and conditions needed for the elimination reaction of haloalkanes
- potassium hydroxide OR sodium hydroxide dissolved in ethanol
- heat under reflux
76
what type of compound do you form in elimination reactions of haloalkanes
alkenes
77
what is the general formula for haloalkanes
CnH2n+1X
78
describe the trend in boiling point in haloalkanes down the group
- increases , because as you go down the group the number of electrons increase , which increases the strength of london forces , requiring more energy to break
79
what type of substances are haloalkanes soluble in
- non polar solvents such as cyclohexanes
80
what conditions do we use for the hydrolysis of haloalkanes by nucleophilic substitution
- aqeuous solution of hydroxide ions
- heat under reflux
81
what do we say when naming a compound with more then OH groups
- 2 : diol
- 3: triol
EXAMPLE : propane - 1 , 2 , 3 triol
82
what is the functional group of an aldehyde and what ending does it have
- AL
- C double bond O and a H on the end
example : propanal
83
what functional group does a ketone have and what ending do we use
C double bond O
- one
84
what rule is there for aldehydes in terms of the positioning of the functional group
- the functional group must always be on the end
- we dont use position numbers
85
what colour is barium in a flame test
apple green
86
what colour does a lithium ion show in a flame test
scarlet red
87
what colour does a sodium ion show in a flame test
yellow
88
89
what is the functional group of an ester and what ending do we use
- C double bond O - O
- ate
89
what rule is there for ketones in terms of the positioning of the functional group
- if there are 5 or more carbon atoms present , numbers to represent the positioning of the functional groups to reduce ambiguity
89
what is a structural isomer
molecules that have the same molecular formula but different structures
89
give all the possible structural isomers for pentane
- pentane
- di - methylpropane
- methyl butane
* NOTE : 2-methyl butane and 3-methyl butane is the same thing as saying methyl - butane , functional groups take priority so they automatically become 1
* ethylpropane can not be one of the isomers , because the name is based on the longest carbon chain there is , which means it will be methyl butane
89
what are stereoisomers
molecules that have the same structural formula but their atoms are arranged differently in space
89
what should you do when working out the structural isomers of compounds that have a functional group
change the positioning of the functional groups and work out the isomers from that point
90
what are the two main groups of stereoisomers
- geometrical isomers
- optical isomers
91
what can single covalent bonds do
they can fully rotate
92
what type of rotation do double covalent bonds have
very restricted rotation
93
what type of isomers can molecules with double covalent bonds have
cis and trans isomers
94
what type of isomers are cis and trans isomers
they are geometrical isomers
95
what two conditions do alkenes have to meet in order to have cis trans isomerism
- both carbon atoms must be attached to two different groups
- the carbon atoms must have at LEAST one group in common
EXAMPLE;
( both carbon atoms must have a bromine atom)
96
how do we determine a cis isomer
the group that both carbon atoms have in common will be on the same side
97
how do we determine a trans isomer
the group that the carbon atoms have in common will be on different sides
98
99
what colour are dichromate ions?
orange
100
what colour are chromium ions?
orange
