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Advanced Higher Chemistry Definitions > Unit 2 > Flashcards

Unit 2 Flashcards

1
Q

Nucleophiles

A

Nucleophiles are negatively charged ions or neutral molecules that are electron rich.

They are attracted towards atoms bearing a partial or full + charge.

They are capable of donating an electron pair to form a new covalent bond.

Nucleophiles are nucleus loving and so nucleophiles are attracted and will attack species with a + charge.

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2
Q

Electrophiles

A

Electrophiles are positively charged ions or neutral molecules that are deficient in electrons.

They are attracted towards atoms bearing a partial or full - charge.

They are capable of accepting an electron pair to form a new covalent bond.

Electrophiles are electron loving and so Electrophiles are attracted and will attack species with a - charge.

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3
Q

2 types of stereoisomer

A

Geometric
Optical

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4
Q

Geometric isomers

A

Arise due to a lack of free rotation around a bond, frequently C=C, but not always.
Must have 2 different groups attached to each of the C atoms.
Non-superimposable

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5
Q

Cis isomer

A

The 2 largest groups are on the same side

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6
Q

Trans isomer

A

The 2 largest groups are on opposite sides.

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7
Q

Optical isomers

A

Arise as they have a chiral centre
They are asymmetric, non-superimposable mirror images of each other.

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8
Q

Chiral

A

4 different groups arranged tetrahedrally around a central carbon atom.

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9
Q

Enantiomers

A

Optical isomers can be described as enantiomers.

They have identical physical and chemical properties except :

Their effect on plane polarised light
Their reaction with other chiral molecules

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10
Q

Racemic mix

A

Contains a 50/50 mix of 2 enantiomers.
This is optically inactive

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11
Q

How to differentiate between 2 optical isomers ?

A

Subject them to plane polarised light.

Each enantiomer will rotate the light by the same angle but in opposite directions.

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12
Q

Drugs

A

Substances that alter the biochemical processes in the body.

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13
Q

Medicine

A

A drug that has a beneficial impact on the body

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14
Q

What do medicines contain ?

A

They contain the drug and often have other added ingredients such as fillers to add bulk or sweeteners to improve taste.

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15
Q

Agonists

A

Agonists MIMIC the natural compound and bind to the receptor molecules to produce a similar response to it.
The drug form ionic bonds with the receptor.

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16
Q

Antagonists

A

Antagonists prevent the natural compound from binding, and so blocks the natural response from occurring.

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17
Q

Enzyme inhibitors

A

Drugs that act on enzymes are classed as enzyme inhibitors and act by binding to the active site of the enzyme. This blocks the reaction normally catalysed here.

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18
Q

Pharmacophore

A

The structural fragment of a drug molecule that allows it to form interactions with a receptor.

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19
Q

Experimental determination of structure

A

Elemental microanalysis
Mass spectroscopy
Infrared spectroscopy
NMR spectroscopy

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20
Q

Elemental microanalysis

A

Used to determine the masses of C, H, O, S and N in a sample of an organic compound, in order to determine its empirical formula.

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21
Q

Empirical formula

A

The simplest ratio of elements in a substance/ molecule.

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22
Q

Mass spectroscopy

A

Used to determine the accurate GFM and structural features of an organic compound.

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23
Q

Infrared Spectroscopy

A

Used to determine and identify certain functional groups in an organic compound.

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24
Q

NMR Spectroscopy

A

Gives information about different chemical environments of H atoms in an organic compound. Allows recognition of how many H atoms are in each environment.

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25
Q

Molecular Orbitals

A

Molecular orbitals are generated when atomic orbitals combine.
The number of molecular orbitals formed is always equal to the number of atomic orbitals that combine.

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26
Q

Sigma bond

A

Molecular orbitals overlap end on.
Single bonds are sigma bonds.

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27
Q

Pi bond

A

Molecular orbitals overlap side on.
Double bonds contain 1 pi bond and 1 sigma bond.
Triple bonds contain 2 pi bonds and 1 sigma bond.

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28
Q

Pi bond V sigma bond

A

Pi bonds are weaker than sigma bonds

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29
Q

Hybridisation

A

Hybridisation is the process of mixing atomic orbitals within an atom, to form a set of new atomic orbitals called hybrid orbitals. These hybrid orbitals are degenerate.

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30
Q

sp3 hybridisation

A

Found in alkANES
Only have sigma bonds.

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31
Q

sp2 hybridisation

A

Found in alkENES
Have sigma and pi bonds.

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32
Q

sp hybridisation

A

Found in alkYNES
Has 2 pi bonds and 1 sigma bond.

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33
Q

HOMO

A

The orbital containing electrons with the highest energy is known as the Highest Occupied Molecular Orbital.

34
Q

LUMO

A

The lowest energy anti-bonding orbital which is vacant is called the Lowest Unoccupied Molecular Orbital.

35
Q

Chromophore

A

A group of atoms within a molecule responsible for the absorption of light in the visible region of the spectrum.

36
Q

Conjugation

A

Alternating single and double carbon to carbon bonds.

37
Q

Reaction of haloalkanes

A

Elimination : to produce an alkene

Nucleophilic Substitution : to produce an ( alcohol, nitrile OR ether )

38
Q

How are haloalkanes classified ?

A

Haloalkanes are classified according to the number of alkyl groups (R) attached to the carbon containing the halogen atom.

39
Q

Haloalkanes

A

Haloalkanes are substituted alkanes in which one or more hydrogen atoms are replaced by a halogen atom.

40
Q

3 types of monohaloalkanes

A

Primary
Secondary
Tertiary

41
Q

Haloalkane Elimination

A

Monohaloalkane + NaOH (eth) ——————————> Alkene

Note : The OH- removes a H atom from a C atom adjacent to the halogen. The halogen is
ejected.

42
Q

Haloalkanes Nucleophilic Substitution reactions

A

Monohaloalkane + NaOH (aq) ——————————> Alcohol

Monohaloalkane + NaCN (eth) ——————————> Nitrile

Monohaloalkane + Alcoholic Alkoxide ——————————> Ether

Note : Alkali metal + Alcohol ——————————> Alcoholic Alkoxide

43
Q

Mechanisms of nucleophilic substitution reactions

A

2 types of mechanisms :

SN1
SN2

44
Q

SN1

A

1st order with respect to the haloalkane
One molecule involved in the slowest step
Tertiary haloalkanes usually undergo SN1
A Trigonal planar CARBOCATION intermediate is formed.

45
Q

What is formed in the SN1 mechanism ?

A

A Trigonal planar carbocation intermediate, stabilised by the inductive effect from the CH3 groups.

46
Q

SN2 mechanism

A

2nd order
2 molecules involved in the slowest step
Primary haloalkanes usually undergo SN2
Proceeds via a 5 centred ( Trigonal bipyramidal ) transition state.

47
Q

What does the SN2 mechanism proceed by ?

A

Via a 5 centred Trigonal bipyramidal transition state

48
Q

Alcohols

A

Alcohols are substituted alkanes, where one or more of the H atoms is replaced with a hydroxyl functional group.

49
Q

Preparation of alcohols

A

Nucleophilic Substitution
Hydration / Addition
Reduction

Monohaloalkane + NaOH (aq) ———————————-> alcohol

                                   conc. H2SO4 Alkene + water  ———————————-> alcohol

Aldehyde/Ketone + LiAlH4 ———————————-> alcohol

50
Q

Reactions of Alcohols

A

Oxidation (using acidified permanganate)
Dehydration (using conc. H2SO4)
Condensation / Esterification (using conc. H2SO4)

Primary alcohol ———————————-> aldehyde

Secondary alcohol ———————————-> ketone

Alcohol ———————————-> alkene

Alcohol + Carboxylic acid ———————————-> ester

51
Q

Physical properties of alcohols

A

Hydroxyl group gives rise to H bonding

H bonding results in a higher boiling point

The polar -OH group allows alcohols to be miscible in water.
As the C chain increases, solubility decreases.

52
Q

Ethers

A

Ethers are substituted alkanes in which a H-atom is replaced with an alkoxy functional group.

R’ ——O—— R”

53
Q

Naming ethers

A

The smaller R—O is given a position and ends in oxy

E.g. methoxy
ethoxy
propoxy etc.

The longest chain is named after an alkane.

E.g. methane
ethane
propane Etc.

54
Q

Preparation of ethers

A

Nucleophilic substitution

Monohaloalkane + alcoholic alkoxide ———————————-> ether

55
Q

Properties of ethers

A

Due to a lack of H bonding, ethers have a lower boiling point than the corresponding isomeric alcohols.

Large ethers are INSOLUBLE in water due to increased molecular size.

56
Q

Uses of ethers

A

Ethers are commonly used as SOLVENTS; since they are relatively INERT chemically and dissolve easily.

57
Q

Preparation of Alkenes

A

Elimination reaction
Dehydration of an alcohol

Monohaloalkane + NaOH(eth) ———————————-> alkene

alcohol ———————————-> alkene + H2O

58
Q

What process do Alkenes react by ?

A

Electrophilic Addition

59
Q

Reactions of Alkenes

A

Hydrogen + alkene ———————————-> alkane

Halogen + alkene ———————————-> dihaloalkane

Hydrogen Halide + alkene ———————————-> monohaloalkane

Water + alkene (acid catalyst) ———————————-> alcohol

60
Q

Markovnikovs Rule

A

Used to determine which of 2 products is in greater yield.

The major product is the one in which the H atom attaches to the C of the double bond that has the greater number of Hs bonded to it.

61
Q

Preparation of Carboxylic acids

A

Oxidation of primary alcohols (using XS acidified dichromate) / aldehydes (using acidified dichromate)

Hydrolysis of ( nitriles, esters or amides ) using an aqueous alkali

Nitrile
Ester + H2O ——————————> Carboxylic acid
Amide

62
Q

Reactions of Carboxylic acids

A

Carboxylic acid

+ metal/base ———————-> salt
+ alcohol ( conc. H2SO4 ) ———————-> ester
+ amine ———————-> alkyl-ammonium salt
+ LiAlH4 ———————-> primary alcohol

63
Q

Amines

A

Amines are organic derivatives of ammonia, in which one or more H atoms are replaced by an alkyl group.

64
Q

How are amines classified ?

A

Classified according to the number of alkyl groups attached to the nitrogen atom.
Can be classed as :
Primary
Secondary
Tertiary

65
Q

Physical properties of amines

A

Primary and secondary amines contain a polar N—H bond and so display H bonding.
As a result, they have higher bpts than isomeric tertiary amines.
Tertiary amines do not display H bonding

All 3 can H-bond with water, thus explaining the appreciable solubility of the shorter chain length amines in water.

66
Q

Reactions of Amines

A

Amine + acid ———————-> alkyl-ammonium salt

Alkyl ammonium salt + HEAT ———————-> amide

67
Q

Benzene

A

C6H6
The simplest member of the class of aromatic hydrocarbons

68
Q

How are benzene rings stable ?

A

The stability of the benzene ring is due to the delocalisation of electrons in the conjugated system.

69
Q

What method does benzene react by ?

A

Electrophilic SUBSTITUTION

The H/ Hs are replaced by atoms or groups (the electrophiles)

70
Q

Phenyl group

A

A benzene ring in which one H atom has been substituted by another group (known as a phenyl group) C6H5

71
Q

Reactions of benzene

A

Alkylation
Sulfonation
Halogenation
Nitration

72
Q

Alkylation

A

Benzene + AlCl3 + R-Cl ———————-> alkylbenzene

73
Q

Halogenation

A

Benzene + AlCl3 + X2 ———————-> halobenzene

74
Q

Sulfonation

A

Benzene + conc. H2SO4 ———————-> benzenesulfonic acid

75
Q

Nitration

A

Benzene + conc. H2SO4 + HNO3 ———————-> nitrobenzene

76
Q

Bond fission

A

The process of bond breaking is known as bond fission.
A bond can break in 2 ways :

Homolytic fission
Heterolytic fission

77
Q

Homolytic fission

A

Occurs when non-polar covalent bonds are broken.
Free radicals are produced.
Caused by HIGH ENERGY UV light.
Can produce multiple undesirable products.

78
Q

Heterolytic Fission

A

Occurs when polar covalent bonds are broken.
Ions are produced.
Double headed arrows are used.

Results in far fewer products than Homolytic fission, and as a result are better suited in the synthesis of organic compounds.

79
Q

sp3 hybridisation

A

One s atomic orbital mixes with three p atomic orbitals to form 4 hybrid orbitals, which are degenerate.

80
Q

sp2 hybridisation

A

One s atomic orbital mixes with two p atomic orbitals to form 3 hybrid orbitals, which are degenerate.

The remaining p orbital is left unhybridised.

81
Q

sp hybridisation

A

One s atomic orbital mixes with one p atomic orbitals to form 2 hybrid orbitals, which are degenerate.

The remaining two p orbitals are left unhybridised.

Advanced Higher Chemistry Definitions (4 decks)

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