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chemistry module 4 > basics + alkanes + alkenes > Flashcards

basics + alkanes + alkenes Flashcards

(53 cards)

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1
Q

general formula definition

A

the simplest algebraic formula of a member of a homologous series

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2
Q

homologous series definition

A

a group of organic compounds with the same functional group and general formula, where each successive member differs by CH2

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3
Q

functional group definition

A

an atom/group of atoms responsible for the characteristic reactions of a compound

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4
Q

hydrocarbon definition

A

a compound containing only C and H atoms

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5
Q

alkyl group definition

A

an organic group with the formula CnH2n+1

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6
Q

aliphatic definition

A

a hydrocarbon compound consisting of straight chains, branched chains or non aromatic rings

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7
Q

alicyclic definition

A

a hydrocarbon compound arranged in non aromatic rings

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8
Q

aromatic definition

A

a compound containing a benzene ring

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9
Q

saturated definition

A

an organic compound with only single C-C bonds

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10
Q

unsaturated definition

A

an organic compound with C=C double bonds, C≡C triple bonds or an aromatic ring

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11
Q

nucleophile definition

A

an electron pair donator

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12
Q

electrophile definition

A

an electron pair acceptor

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13
Q

structural isomerism definition

A

molecules with the same molecular formula but different structural formulae

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14
Q

what are the 3 types of structural isomerism

A
  • chain isomerism
  • positional isomerism
  • functional isomerism
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15
Q

chain isomerism definition + example

A

molecules with the same molecular formula but different carbon arrangements in straight or branched chains
e.g. butane and methylpropane

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16
Q

positional isomerism definition + example

A

molecules with the same molecular formulas and carbon skeleton and functional group, but different positions of the functional group
e.g. but-1-ene and but-2-ene

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17
Q

functional isomerism definition

A

molecules with the same molecular formulae but different functional croups
e.g. butene and cyclobutane

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18
Q

what are the 3 naming steps

A

1- identify longest carbon chain/longest chain with priority functional group
2- identify functional groups and the numbered C they are attached to
3- arrange in alphabetical order

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19
Q

what is the priority ranking for naming/identifying carbon chains - from lowest to highest

A

carboxylic acid (HIGHEST)
ester
amide
nitrile
aldehyde
ketone
alcohol
amine
alkene
alkyne
alkane (LOWEST)

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20
Q

homolytic fission definition

A

when a bond is broken and each bonding atom received on electron from the bonded pair, forming 2 radicals

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21
Q

heterolytic fission definition

A

when a bond is broken and just one bonding atom received both electrons from the bonded pair

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22
Q

radical definition

Study These Flashcards
A

a species with an unpaired electron

23
Q

3 types of reactions

Study These Flashcards
A

elimination
addition
substitution

24
Q

elimination definition

Study These Flashcards
A

a reaction involving the removal of a small molecule from a larger one, usually a single bond is turned into a double bond

25
addition definition
a reaction where 2 reactants join to form one product, usually a double bond is turned into 2 single bonds
26
substitution definition
a reaction where an atom/molecule is replaced by another atom/molecule
27
what is the shape and bond angle around a C atom in alkanes
tetrahedral angle = 109.5
28
explain the trend in boiling points in alkanes
as chain length increases boiling point increases as longer chains = more atoms with electrons = more london forces which require more energy to overcome
29
explain how branching affects boiling point
as branching increases boiling point decreases as branched alkanes cannot pack as closely together = decreased london forces between molecules which requires less energy to overcome
30
why do alkanes have low reactivity
C-C and C-H bond enthalpies are high so lots of energy is needed to break them these bonds also have a low polarity so they do not attract nucleophiles or electrophiles easily
31
give 1 use for alkanes
complete combustion of alkanes is used as fuel
32
why might incomplete combustion occur + what is dangerous about it
incomplete combustion occurs in a limited supply of oxygen it forms CO which is a toxic gas as it binds to haemoglobin irreversibly therefore preventing oxygen transport around the body
33
what are the 3 stages in radical substitution
initiation - the formation of a radical propagation - maintaining radical concentration termination - loss of radical concentration
34
what are limitations of radical substitution
it doesn't produce a very high yield of product, especially if a very specific compound is needed, due to: - further substitution in excess halogen forming di/tri haloalkanes - substitution can occur at different positions on the chain, products could be various isomers - impurities as multiple products are formed in the termination steps so the product needed is mixed up with other stuff too
35
a radical substitution question may give you a compound and then ask how many different isomers can be formed with just a single substitution - how can you work this out
the answer should be the same as the number of proton environments in the molecule - trick! - good to think of as you might miss an isomer - this will only work for single substitutions !
36
summarise the 1 main reaction of alkanes
halogenation via free radical substitution with a halogen under UV to make haloalkanes
37
what is the shape and bond angle around a double bond in an alkene
triagonal planar angle = 120
38
pi bond definition
a pi bond is formed by the sideways overlap of electrons in adjacent p-orbitals
39
what bonds make up a C=C double bond
1 sigma bond and 1 pi bond
40
stereoisomerism definition
molecules that have the same molecular and structural formulae but different spatial arrangement
41
what are the 2 types of stereoisomerism
E/Z isomerism and optical isomerism
42
why does stereoisomerism occur in alkenes
this is because double bonds restrict rotation around the C atom E - high priority groups opposite each other Z - high priority groups next to each other
43
what conditions are needed for E/Z isomerism
a C=C double bond with 2 different groups attached to each carbon of the double bond
44
cis-trans isomerism definition
a special case of E/Z isomerism where one of the groups on each carbon is a H atom cis - Z - H atoms next to each other trans - E - H atoms opposite each other
45
outline the inductive effect
when a carbocation has alkyl groups attached (known as electrodonating groups) this will stabilise the carbocation, making it less positively charged this is because alkyl groups push electron density towards the carbocation making it energetically more stable therefore in terms of stability tertiary carbocation > secondary carbocation > primary carbocation
46
state markownikoffs rule
during electrophilic addition of HY to asymmetrical alkenes the H will bond to the C atom bonded to the most H atoms, whereas the other group Y will bond to the most substituted C atom (bonded to the least H atoms/most alkyl groups) which is the more stable carbocation therefore will remain as an intermediary long enough for the next step of the reaction to occur if the addent contains 2 halogens e.g. Br-F the more electronegative halogen will bond to the most substituted C atom - in this case F
47
why are alkenes more reactive than alkanes
pi bonds have lower enthalpy than sigma bonds, so less energy is needed to break a double bond into a single bond than to break a single bond also double bonds have high electron densities therefore are more polarising and attract electrophiles
48
summarise 3 main reactions of alkenes
- hydrogenation via electrophilic addition with H2 + Ni catalyst to become alkanes - electrophilic addition with hydrogen halides to become haloalkanes - hydration via electrophilic addition with steam + H2SO4 catalyst at high temps and pressure to become alcohols
49
QUALITATIVE ANALYSIS OF ORGANIC COMPOUNDS outline the test for alkenes + equation
- react with bromine water POSITIVE= the solution decolourises from orange-brown - colourless alkene + Br2(aq) >> dibromoalkane
50
polymer definition
a long chain molecule made of many repeating units called monomers
51
monomer definition
small molecules which can react together to form polymers
52
what type of polymerisation can alkenes undergo + why
addition polymerisation by breaking the double bod into a single bond
53
give 3 sustainable ways to process waste polymers
- combust as a fuel source to produce energy - use as organic feedstock for the production of plastics - removal of toxic wastes formed from other reactions

chemistry module 4 (2 decks)

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