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module 4 Flashcards

1
Q

what are the uses of organic materials

A

domestic central heating

electrical generation

powering many forms of transport

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2
Q

define a hydrocarbon

A

compound containing carbon and hydrogen only

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3
Q

define a homologous series

A

family of compounds with similar chemical properties whose successive members differ by CH2

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4
Q

define a functional group

A

part of a molecule that is largely responsible for the molecule’s chemical properties

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5
Q

define an aliphatic compound

A

carbon joined together in straight or branched chains or non-aromatic rings

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6
Q

define an alicyclic compound

A

carbons joined together in ring structure

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7
Q

define an aromatic compound

A

carbons joined in a benzene ring

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8
Q

how are covalent bonds broken?

what is the difference between these two types. give definitions.

A

broken by homolytic or heterolytic fission

homolytic – each of the bonded atoms takes 1 of a shared pair of electrons (each atom has a single unpaired electron, so they become a radical

heterolytic – one of the bonding atoms takes both electrons from the bond
the ‘taker’ becomes a negative ion
the ‘bystander’ becomes a positive ion~

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9
Q

what do curly arrows show

A

movement of electron pairs

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10
Q

what are the three types of reaction

A

addition - 2 reactants form one product

substitution - atom/group of atoms(goa) replaced by different atom/goa

elimination - removal of a small molecule from a larger one
one reactant forms 2 products

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11
Q

what are the uses of alkanes

A

used as fuel

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12
Q

describe the formation of a sigma bond

A

result of the overlap of 2 orbitals (1 from each bonding atom)

sigma has 2 electrons shared between atoms

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13
Q

how does the length of the chains in an alkane affect the boiling point

A

as the chain length increases,
there are greater LDF,
so the boiling point increases

also, the surface area increases,
so there is more surface contact,
so there is more LDF

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14
Q

how does the presence of branches affect the boiling point

A

branched alkanes have less points of contact so they have less LDF

branches prevent molecules from getting close as straight chain molecules so there are less LDF

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15
Q

explain why alkanes have a low reactivity

A

C-C and C-H sigma bonds are strong

C-C non-polar

C-H electroneg. is similar so are considered non-polar

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16
Q

what conditions are required for radical substition

A

UV light and high temperature

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17
Q

how does the propagation step end in radical substitution?

A

when 2 radicals collide

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18
Q

what allows propagation to cycle into a chain reaction

A

radical produced in 2nd step

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19
Q

what are the limitations of free radical substitution

A

has problems that limit its importance for synthesis of one organic compound

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20
Q

what are the conditions required for a compound to have E/Z isomerism

A

molecule must have a C=C and different groups attached to each C in the C=C

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21
Q

what’s the difference between cis/trans and E/Z isomerism

A

in cis/trans isomerism, one of the attached groups on one carbon must also have the same group attached to the other carbon

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22
Q

give a brief synopsis on the cahn-ingold-prelog rules

A

atoms are given priority based on their atomic number

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23
Q

what happens if the 2 groups attached to the carbons have the same atomic number

A

group given a higher priority at the first point of difference in the group

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24
Q

describe the bonding in alkenes in terms of the double bonds

A

for each C of the double bond, 3 or 4 e- are used in 3 sigma bonds
(1 to other C, other 2 to 2 other atoms)

this leaves 1e- (in a p-orbital) on each C of the double bond

pi bond forms by the sideways overlap of 2 p-orbitals (1 from each carbon)

pi electron density concentrated above and below the plane

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25
what makes the alkene and alkanes different in terms of movement
presence of pi bonds prevents rotation because it locked the carbon atoms of the double bond in position
26
explain the trigonal planar shape of the C in the double bond
3 regions of e- density around carbon 3 regions repel each other so it's 120 degrees atoms are in the same place
27
what makes the alkenes more reactive than alkanes
C=C pi bond is outside of bond, so more exposed than e- in sigma bonds so the pi bond readily breaks more easily than sigma bond
28
what are the conditions required for hydrogenation what type of reaction is it
nickel catalyst 423 K addition
29
what are the conditions required for halogenation what type of reaction is it
RTP addition
30
what are the conditions required for hydration what type of reaction is it
steam acid catalyst (phosphoric acid) addition
31
what allows electrophilic addition in alkenes
double bond represents region of high electron density due to pi electrons which attracts electrophiles
32
define an electrophile
compound attracted to electron dense areas accepts a electron pair (example is a positive ion)
33
how can non-polar molecules do electrophilic addition
pi electrons interact with electrons in X-X polarisation of X-X forms induced dipole electron pair of pi attracted to less electronegative X end
34
order carbocations of their stability what makes a carbocation stable
primary < secondary < tertiary linked to electron-drawning ability of alkyl groups each alkyl donates and pushes electrons towards positive charge of carbocation positive charge spreads over alkyl more alkyls allows charge to spread out more, making the ion more stable
35
what are some characteristics of alcohols when compared to alkanes
lower volatility higher melting point higher water solubility differences become smaller the higher the chain length
36
compare the polarity and the intermolecular forces of alkanes and alcohols
in alkanes, C-H bonds have similiar electronegativity so are non-polar, thus have weak LDF in alcohols, O-H are polar electronegativity is different (so polar molecule) the molecule has weak LDF and stronger hydrogen bonds between O-H groups
37
explain alcohols low volatility
hydrogen bonds hold the molecules together requiring more energy to overcome LDF in alkanes thus alcohols have low volatility
38
explain why solubility decreases as the chain length of alcohols increases
influence of the OH group decreases
39
name the reactions of the alcohols
combustion oxidation dehydration substitution
40
what causes the change in color of the oxidising agent in oxidation of alcohols
reduction of dichromate (VI) ions --> chromium (III) ion
41
give the molecular formula of the oxidising agent used in oxidation of alcohols
K2Cr2O7/H2SO4
42
describe conditions for the dehydration of alcohols
heat under reflux acid catalyst --> alkene
43
describe the substitution reaction of an alchol
Hydrogen halide produced in reaction: NaX + H2SO4 --> HX + NaHSO4 then: alcohol + HX --> haloalkane + H20 reflux
44
describe the conditions and reaction of an alkane becoming a haloalkane
radical substitution UV light + halogen
45
describe the oxidation of primary alcohol
distil --> aldehyde reflux --> carboxylic acid
46
describe the oxidation of secondary alcohol
reflux --> ketone
47
what is dehydration of an alcohol an example of what type of reaction
elimination
48
explain why the C-X bond in haloalkanes is polar
electronegativity difference electron pair is closer to more electronegative halogen so the C-X is polar
49
what allows nucleophilic substitution in haloalkanes
the C in the C-X is less electronegative so electron-deficient which attracts nucleophiles
50
what is used in nucleophilic substitution of haloalkanes
ethanol solvent allows the (insoluble) haloalkane and the water to mix and produce a single layer
51
what type of fission breaks the C-X bond in nucleophilic substitution
heterolytic fission produces a X- (negative ion)
52
how is the rate of hydrolysis measured
adding silver nitrate Ag+ + X- form AgX precipitate
53
the rate of hydrolysis increases as ...
the strength of the C-X bond decreases
54
how is plastic made and why
by polymers cheap and polymers are unreactive hard to dispose, which creates problems
55
give an example of non-biodegradeable polymers
alene-based polymers
56
what is the first way of disposing polymers
combustion for energy production plastics are burnt so the chemical energy transferrs but CO2 produced (greenhouse gas)
57
what are the two another ways of disposing polymers
use as chemical feedstock for production removal of toxic waste production depending on the plastic, toxic gas produced
58
which halide solution with silver is soluble in dilute and concentrated ammonia solution
AgCl -- soluble in both Agr -- soluble in conc. ammonia solution
59
describe the ozone layer
high conc. of ozone molecules in a layer of stratosphere which absorbs high proportion of UV radiation is continually formed and broken down at the same rate
60
what are the different types of UV and what is their different absorptions by ozone
UVa = 5% absorbed UVb = 95% absorbed UVc = 100% absorbed
61
how does ozone depletion link to skin cancer
more UV reaches the earth's surface higher risk of skin cancer
62
describe chloroflourocarbons
developed for use as refrigerants low reactivity high volatility non-toxic
63
how is the chlorine radical able to destroy ozone
1 chlorine radical destroys ~100,000 ozone molecules
64
give the reaction for the breakdown of ozone with radicals
R. + O3 -> RO + O2 RO + O -> R + O2 O3 + O -> 2O2
65
give the reaction for the breakdown of ozone with nitrogen monoxide
NO. + O3 -> NO2. + O2 NO2. + O -> NO. + O2 O3 + O -> 2O2
66
describe the montreal protocol
effects of CFCs on ozone layer were established in 1970s
67
what are some alternatives for CFCs
HCFC Has C-H bond which degrades before it reaches the stratosphere Hydrocarbons
68
describe the greenhouse effect
electromagnetic radiation from sun reaches earth's atmosphere earth's surface absorbs this and emits it as IR greenhouse gases absorbs IR and some gases into space earth's atmosphere warms up
69
what happens to molecules when they absorb IR
(cov) bonds vibrate more
70
the greenhouse effect of a gas depends on ...
conc. of it in atmosphere its ability to absorb IR
71
what is mass sprectrum used for
identify unknown compounds determine abundance of an isotope of an element gain more info on the structure of a molecule

chemistry (8 decks)

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