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A level Chemistry OCR > 4.1 Basic Concepts And Hydrocarbons > Flashcards

4.1 Basic Concepts And Hydrocarbons Flashcards

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1
Q

General formula

A

An algebraic formula that can describe any member of a family of compounds

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2
Q

Empirical forumla

A

Simplest whole number ratio of atoms of each elemnt in a compound

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3
Q

Molecular formula

A

Actual number of atoms of each element in a molecule

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4
Q

Structurual forumla

Like for Butan-1-ol

A

Shows arrangement of atom carbon by carbon, with the attached hydrogen and functional group

CH3CH2CH2CH2OH
or
CH3(CH2)30H

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5
Q

Skeletal formula

A

Shows the bond of the carbon skeleton only, with any functional groups. The hydrogen and carbon atoms aren’t shown. (zig zag and ring ones)

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6
Q

Displayed forumla

A

Shows how all the atoms are arranged, and all the bonds between them

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7
Q

Branched alkanes prefix or suffix

General formula for alkanes?

A

alkyl-(-yl)

CnH2n+2

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8
Q

haloalkanes prefix or suffix

A

chloro-/bromo-/iodo-

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9
Q

aldehyde prefix or suffix

A

-al

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10
Q

ketones prefix or suffix

General formula for ketones?

A

-one

CnH2nO

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11
Q

cycloalkanes prefix or suffix

General formula for cycloalakane?

A

cyclo-…-ane

CnH2n

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12
Q

carboxyclic acid prefix or suffix

General formula for carboxcylic acid?

A

-oic acid

CnH2n+1COOH

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13
Q

ester prefix or suffix

A

alkyl-…-anoate

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14
Q

Structural isomers

A

Compounds with the same molecular formula but different structural formula

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15
Q

Homolytic fission

A

Breaking a covalent bond to form two radicals

Where each bonding atom is receiving one electron from the bonded pair

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16
Q

Heterolytic fission

A

Breaking a covalent bond to form two oppositely charged ions

where one bonding atom receives both electrons from the bonded pair

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17
Q

Curly Arrow

A

Shows the movement of an electron pair during a reaction

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18
Q

What are the 3 steps in free radical substitution

A
  1. initiation
  2. propagation
  3. termination
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19
Q

what is the initiation equations for methane and chlorine to give chloro-methane and hydrogen chloride

A

CL2 –> 2CL.

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20
Q

what are the 2 propagation equations for methane and chlorine to give chloro-methane and hydrogen chloride

A

Cl. + CH4 –> CH3. +HCl

Cl2 + CH3. –>CH3Cl +Cl.

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21
Q

what are the termination step equations for methane and chlorine to give chloro-methane and hydrogen chloride

A

Cl. + Cl. –> Cl2
Cl. +CH3. –>CH3Cl
CH3. + CH3 –> C2H6

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22
Q

Why do branch isomers have lower MP then straight chained isomers?

A

Can’t pack close to each other and smaller molecular surface areas
so less surface contact between molecules…
less induced dipole forces…
so less energy to break force

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23
Q

Why does BP increase as chain lengths increase for hydrocarbons?

A

Stronger intermolecular forces

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24
Q

Why does adding carbon to a chain start to become less significant in terms of boiling point?

A

As the mass is increasing by a small percentage each time

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25
Q

Homologous series

A

A series of organic compounds having the same functional group but with each successive member differing by CH2

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26
Q

Functional group

A

A group of atoms responsible for the characteristic reaction of a compound

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27
Q

What are the general formula for alkenes and alcohols?

A

Alkene: CnH2n

Alcohol: CnH2n+1 OH

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28
Q

Aliphatic

A

A compound containing carbon and hydrogen joined together in straight chains, branched chains or non-aromatic rings (have no benzene ring)

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29
Q

Alicyclic

A

An aliphatic compound arranged in non-aromatic rings with or without side chains (have a ring but not a benzene ring)

30
Q

Aromatic

A

A compound containing a benzene ring

31
Q

What is meant by a saturated compound?

A

Single carbon-carbon bonds only

32
Q

Unsaturated compound

A

The presence of multiple carbon-carbon bonds, including c=c bonds, c-c and aromatic rings.

33
Q

Describe alkanes

A

Saturated hydrocarbons containing single C-C and C-H bonds as sigma bonds; free rotation of the sigma bond

34
Q

What is a pie bond?

A

Sideways overlap of adjacent p-orbitals above and below the bonding C atoms.

35
Q

What is an electrophile?

A

An electron pair acceptor

36
Q

What is a radical?

A

A species with an unpaired electron

37
Q

What shape and bond angle is around a carbon in an alkane?

A

tetrahedral, 109.5, because of 4 bonding pair electrons repelling each other equally

38
Q

Whats the equation for combustion of propane?

A

C3H8(g) + 502(g) –> 3C02(g) + 4H20(g)

39
Q

Combustion reactions happen between what state?

and what does this mean has to happen first?

A

Gases, so liquid alkanes must be vaporised first.

Smaller alkanes are more volatile, so they’ll burn more easily too

40
Q

What releases more energy larger alkanes or smaller alkanes and why?

A

larger alkanes releases lots more energy per mole as they have more bonds to react. So alkanes are excellent fuels

41
Q

Whats the danger when alkanes burn in limited oxygen?

A

CO is produced. It is poisonous.

42
Q

Why is CO (carbon monoxide) poisonous?

A

CO is better at binding to haemoglobin than oxygen, so it binds before the oxygen can. so less oxygen is being carried around body, leading to oxygen deprivation.

43
Q

Whats required for free radical substitution?

A

UV light-photo dissociation

44
Q

What are the problems with free radical substitution?

A

The problem with this is further substitution can occur and substitution can occur in different positions in molecules with more than 1 carbon

45
Q

Describe an alkene

A

unsaturated hydrocarbons containing C=C compromising of a π-bond and σ-bond

46
Q

What is a σ-bond?

A

σ-bond: Overlap of orbitals directly between the bonding atoms

47
Q

What is a π-bond?

A

π-bond: Sideways overlap of adjacent p-orbitals above and below the bonding C atoms

48
Q

What is the shape and bond angle around a C=C?

A

Trigonal planar shape, 120 degrees, 3 bonding pairs, no lone pairs, electron pair repulsion theory (the double bond counts at 1 electron pair)

49
Q

What is weaker π-bond or σ-bond?

A
  • π-bond are much weaker because the electron density is spread out above and below the nuclei.
  • This means that the electrostatic attraction between nuclei and shared pair of electrons is weaker,
  • so π-bond have relatively low bond enthalpy.
50
Q

Why are alkanes not as reactive as alkenes?

A

Only contain C-C and C-H σ bonds, which have high bond enthalpy and so are difficult to break

The bonds are also non polar so they don’t attract nucleophiles or electrophiles

51
Q

Why are alkenes more reactive?

A

C=C contain both π-bond and σ-bond

The C=C contain 4 electrons so it has a higher electron density and the π-bond also sticks out above and below the rest of the molecule

These 2 facts mean π-bond is likely to be attacked by electrophiles

The low bond enthalpy of the π-bond also contribute to reactivity of alkenes

52
Q

What industry make use of the highly reactive alkenes?

A

Petrochemical

53
Q

What is a steroisomer?

A

same structural formula but different arrangement in space

54
Q

E/Z isomerism

A

an example of stereo isomerism, due to restricted rotation about a double bond and two different groups attached to each carbon atom of the C=C group

55
Q

Cis–trans isomerism

A

A special case of E/Z isomerism in which two of the substituent groups attached to each carbon atom of the C=C group are the same

56
Q

How do you identify E/Z stereoisomer

A
  • First see if its a steroisomer (when two double bonded carbon atoms each have 2 different atoms or groups attached)
  • Its E if the highest priority (look at atomic mass) groups are diagonal

its Z if highest priority are both above or both below the c=c

57
Q

How do you identify if its cis or trans?

A

cis identical groups are on the same side of the c=c

Trans identical groups are on opposite side of the c=c bond

58
Q 
Describe addition reaction of alkenes with hydrogen
reagent: 
condition: 
Product: 
Equation: 
use:
A

reagent: hydrogen
condition: Nickel catalysts, 150.c
Product: Alkane
Equation: C2H4(g) + H2(g) –> C2H6(g)
use: Margarine manufacture

59
Q 
Describe addition reaction of alkenes with steam
reagent: 
condition: 
Product: 
Equation: 
use:
A

reagent: Steam
condition: catalyst-phosphoric acid, 300.c, 60-70 atm
Product: alcohol
Equation: C2H4(g) + H20 (g) C2H50H
use: Ethanol manufacture

60
Q

What tests for the presence of a double C=C?

A

Bromine

Shake an alkene with orange bromine water,, the solution quickly decolourises
This is because bromine is added across the double bond to form a colourless dibromoalkane

61
Q

How does electrophilic addition reactions happen?

A

The double bond has got plenty of electrons and is easily attacked by electrophiles

electrophiles are electron pair acceptors

electrophiles include positively charged ions (H+, N02+) and polar molecules

62
Q

Halogen and alkene form…

What type of reaction is it?

A

Dihaloalkane

Electrophilic addition reaction

63
Q

What is a carbocation?

A

Organic ion containing a positively charged carbon atom

64
Q

Describe the mechanism for halogen bromine reacting with ethene

A

The double bond repels the electrons in Br2, Polarising Br-Br

Heterolytic fission of Br2. The closer Br gives up the bonding electrons to the other Br and bonds to the C atom. (Arrow from double bond to Slightly positibe Br, arrow from Br-Br bond to slight negative Br

You get positively charged carbocation intermediate
The Br- now zooms over (show unpaired electron pair on Br with negative charge, draw arrow from electron pair to + on carbocation)

and bonds to the other C atom forming
1, 2-dibromoethane

65
Q

What’s markonikoffs rule?

A

The major product from addition of a hydrogen halide (HX) to an unsymmetrical alkene is the one where hydrogen adds to the carbon with the most hydrogens already attachedx

66
Q

Whats most stable, tertiary, secondary or primary cation?

A

Tertiary carbocation intermediate

67
Q

Whats useful about polymers?

A

Very un-reactive so good for pans window coating frame

68
Q

How are plastics disposed of?

A

organic feed stock, combustion, recycle, landfill

OCRL

69
Q

Why does burning waste plastics need to be carefully controlled?

A

To reduce toxic gasses
polymers that contain chlorine (such as PVC) produces HCl when burned
Waste gasses is passed through scrubbers which neutralise gases like HCl by allowing them to react with a base.

70
Q

How can biodegradable polymers made decomposable?

A

renewable raw materials such as Starch or oil fractions,

71
Q

Photo-degradable polymers what are they?

A

polymers that decompose when exposed to sunlight

A level Chemistry OCR (15 decks)

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