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Chemistry - Mrs McDougal > Organic Chemistry 2 > Flashcards

Organic Chemistry 2 Flashcards

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1
Q

Give the functional group and suffix for carboxylic acids

A
  • COOH
  • oic acid
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2
Q

Boiling points of carboxylic acids compared to alkanes

A
  • Much higher
  • CA contain hydrogen bonding + Van der Waals
  • Alkanes only contain Van der Waals
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2
Q

Describe and explain the solubility trend for carboxylic acids

A
  • Higher Mr = Lower solubility
  • Low Mr acids can hydrogen bond with water
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3
Q

Describe how to make carboxylic acids

A
  1. Oxidise a primary alcohol to form an aldehyde
  2. Oxidise the aldhehyde (under reflux with acidified potassium dichromate) to from carboxylic acid
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4
Q

What type of acids are carboxylic acids and what do they react with?

A

Weak acids

React with:
- Bases
- Alkalis
- Metals
- Carbonates
(Just slower than normal acids)

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5
Q

What is the functional group and suffix for esters?

A
  • COO
  • anoate
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6
Q

Give some uses of esters

A
  • Food flavourings
  • Perfumes
  • Solvents
  • Plasticisers
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7
Q

How are esters made?

A

Esterification

Carboxylic acid + alcohol -> ester + water

  • Reversible reaction
  • Slow
  • Requires warm and conc HCl or H2SO4 catalyst
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8
Q

How are esters collected from the products of esterification?

A
  • Ester can be distilled off
  • Boiling point is lower as it doesn’t have hydrogen bonding like water
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9
Q

Describe standard hydrolysis of esters

A

Opposite of esterification

ester + water -> carboxylic acid + alcohol

  • Reversible reaction
  • Slow
  • Requires warm and conc HCl or H2SO4 catalyst
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10
Q

Describe the alternative method to hydrolyse esters

A

Saponification

ester + alkali -> carboxylate salt + alcohol

  • Not reversible
  • Faster
  • Requires warm, alkali conditions
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11
Q

How are soaps made?

A
  • Saponification
  • By heating fats/oils with sodium or potassium hydroxide
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12
Q

How do soaps work?

A
  • The hydrophilic part of the molecule attracts to the water
  • The hydrophobic part of the molecule attracts to the fat
  • The molecule then pulls the fat off the fabric and into the water
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13
Q

What is biodiesel?

A

A fuel that can be used in diesel engines in place of diesel made from crude oil

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14
Q

How are bio-diesels made?

A

Transesterifcation

Reacting the lipids in vegetable oils with methanol using a potassium hydroxide catalyst

Lipid + methanol -> methyl esters of fatty acids (biodiesel) + glycerol

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15
Q

What are arenes?

A

Homologous series of hydrocarbons based on benzene (C6H6)

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16
Q

Describe the structure of benzene

A
  • Planar molecule
  • 6 carbons form a hexagonal ring with one H atom bonded to each
  • One unused electron in the P orbital of each carbon
  • P orbitals overlap and electrons become delocalised
  • Form an ‘electron cloud’ above and below the plane of the molecule
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17
Q

List the evidence to support the delocalised benzene structure

A
  • Addition reactions
  • Bond lengths
  • Enthalpy of hydrogenation values
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18
Q

Describe how addition reactions support the delocalised structure of benzene

A

If benzene instead contained 3 C=C, it would readily undergo addition reactions

But it doesn’t

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19
Q

Describe how bond lengths support the delocalised structure of benzene

A

Measurements from x-ray diffraction show that carbon carbon bonds in benzene are all the same length

If the original structure was right there would be 3 long bonds (C-C) and 3 short (C=C)

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20
Q

Describe how enthalpy of hydrogenation values support the delocalised structure of benzene

A

Benzene is 152 kJ per mol stable than the original structure would be

This is because of the ‘electron cloud’ and the delocalisation stability

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21
Q

What are the uses of nitration?

A
  • Production of explosives
  • Producing aromatic amines which are then used to make industrial dyes
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22
Q

Define aliphatic amines

A

Amines with alkyl groups attached to the N

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23
Q

Define aromatic amines

A

Amines with the N joined directly to a benzene ring

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24
Q

Describe the basic nature of amines

A
  • Bronsted-Lowry bases
  • Lone pair on the N atom can readily accept a proton
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25
Q

List the base strength of amines

A

Aliphatic amines > NH3 > aromatic amines

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26
Q

Describe why aliphatic amines are so basic

A
  • Alkyl groups push electrons towards the N (a positive inductive effect)
  • Increases the availability of the N lone pair
  • Increases ability to accept H+
27
Q

Describe why aromatic amines are not so basic

A
  • The N lone pair is partially delocalised into the benzene ring
  • Reduces availability of the N lone pair
  • Reduces ability to accept H+
28
Q

Describe the composition of an amino acid

A
  • Amine group
  • Carboxylic acid group
  • R group
29
Q

What is an alpha amino acid?

A

An amino acid with 1 carbon between the amine group and the carboxylic acid group

30
Q

Define zwitterion

A

An ion that has two charges at the same time

31
Q

Describe the charge on an amino acid

A
  • In the solid state, all amino acids exist as zwitterions
  • H falls off carboxylic acid group and attaches to amine group
  • Positive charge on N, - charge on O
32
Q

Describe and explain the physical properties of amino acids

A
  • Ionic
  • Have high melting points
  • Solid at room temp
  • Soluble in water
33
Q

List the reactions that can be undergone by the amine group of an amino acid

A
  • Protonated by acids
  • Acylation with acyl chloride/acid anhydride
  • Nucleoophilic substitution with haloalkanes
34
Q

List the reactions that can be undergone by the carboxylic acid group of an amino acid

A
  • Deprotonated by bases
  • Acylation
  • Esterification with alcohols
35
Q

Describe the preparation of aromatic amines

A

The reduction of aromatic nitro compounds
* Nitrobenzene + 6[H] -> Phenylamine +2H20
* To this reaction you must add Sn and HCl

  • The Sn and HCl form hydrogen which reduces the nitrobenzene
  • Intially a salt is formed so the NaOH is added to liberate the free amines
36
Q

The reaction of NH3 and a haloalkane produces amines put is not commonly used. Why not?

A

This produces a mixture of primary, secondary and tertiary amines as well as quaternary salts
* If an excess of NH3 is used, then it is mostly primary amine
* If an excess of haloalkane is used, then it is mostly quaternary salt

37
Q

Define addition polymer

A

Long chain molecules formed from lots of small molecules (monomers) join together to form a polymer, with nothing elese formed

38
Q

Define condensation polymers

A

Long chain molecules formed from lots of small molecules (monomers) joined together to form a polymer with another small molecule formed as well

39
Q

Describe how polyesters are formed

A
  • Dicarboxylic acids + diols
  • In the presence of a strong acid or specific enzyme
40
Q

Describe how polyamides are formed

A
  • Dicarboxylic acids + diamines
  • In the presence of a strong acid or specific enzyme
41
Q

What is the main problem with addition polymers?

A
  • Generally unreactive and chemically inert
  • So do not biodegrade
42
Q

List the 3 methods of non-biodegradable polymer disposal and their problems

A
  1. Landfill - Land is limited
  2. Incineration - Greenhouse gases such as CO2 and toxic gases are produced
  3. Recycling - Seperation of pure polymers can be expensive and difficult
43
Q

Why are condensation polymers better for the environment?

A
  • Biodegradable
  • Amide or ester linkages can be reacted with acids or bases in hydrolysis
44
Q

Explain the difference between a polypeptide and a protein

A
  • <50 amino acids = polypeptide
  • 50+ = protein
45
Q

Describe the bonding present in the secondary structure of a polypeptide

A
  • H bonding
  • N and O are very electronegative so C=O and N-H are polar
  • Lone pair on O of amino aci attracted to the partially postivive H on another
46
Q

What is a disulphide bond?

A

A covalent bond between two sulphurs

47
Q

How do enzymes work as biological catalysts?

A
  • Lock and key theory
  • Active sites are stereospecific to substrates
48
Q

How does enzyme inhibition work?

A
  • Similar shape to enzyme active site
  • Block the active site so no substrate can fit
49
Q

Give the 4 DNA bases in their pairs

A
  • Adenine - Thymine
  • Guanine - Cytosine
50
Q

Describe how nucleotides form

A
  • Phospate attachs on the 5’ carbon in the sugar
  • Bases attach to the 1’ carbon
51
Q

How do you number the carbons in a deoxyribose sugar?

A

Number from the right of the oxygen and move clockwise

52
Q

What is cisplatin and how does it work?

A
  • cis-diamminedichloroplatinum (II)
  • Cisplatin attaches to N atoms of guanine bases in a ligand replacements reaction
  • This stops the DNA strands unwinding so DNA replication cannot happen
  • Cancer cells can no longer divide
53
Q

Describe the side-effects of treatment with cisplatin

A
  • Hair loss
  • Nausea
  • Immunosuppression
54
Q

Give some ways of reducing the side-effects of treatment with cisplatin

A
  • Use lowest therapeutic dose
  • Develop new drugs
  • Find ways of targeting cancer cells directly
55
Q

Define stationary phase

A

The solid used chromatography (or a liquid supported on a solid)

56
Q

Define mobile phase

A

The liquid or gas used in chromatography

57
Q

Describe paper/thin layer chromatography

A
  • A pencil is drawn near the bottom of the paper
  • A small drop of the mixture is placed on the line
  • Solvent is added to just below the line
  • Left to stand in a covered beaker
  • Different components move up the paper at different rates depending on their relative affinities for the MP or SP
58
Q

Give the Rf equation

A

Rf = Distance spot moved / Distance solvent moved

59
Q

What if substances separated by paper chromatography are colourless?

A

Can be revealed using UV light or chemical staining agents such as iodine or ninhydrin

60
Q

Describe column chromatography

A
  • A column is filled with an inert solid (SP)
  • Sample mixture introduced at top
  • A liquid solvent (eluent) is then applied from the top (MP)
  • As the solvent runs down the column the different substances in the mixture will separate out depending on their relative affinities for the MP or SP
  • Retention time = time to come out of the bottom of the column
61
Q

Describe gas-liquid chromatography

A
  • Long coiled tube packed with a solid (SP)
  • Sample is vapourised and injected into the instrument
  • An inert gas (MP) carries the sample through the instrument under pressure and at high temp
  • Retention time = time to travel through tube
  • Components separated by GC re often analysed by mass spectrometer as they leave tube
62
Q

What does no. of signals, position of the signals and height of signals indicate in 13C NMR?

A
  • No. of signals - No. of c environments
  • Position of signals - Chemical environment of C’s
  • Heights of peaks are not relevant
63
Q

What does no. of signals, position of the signals and height of signals indicate in 1H NMR?

A
  • No. of signals - Chemical environment of H’s
  • Position of signals - Chemical environment of H’s
  • Height of peaks - Relative to the number of H’s causing the signal
64
Q

What is the zero value in 1H NMR?

A

All 1H NMR is comparative to the reference compound tetramethylsilane (TMS)

65
Q

Why is tetramethylsilane used as the reference compound for 1H NMR?

A
  • Non-toxic
  • Inert
  • Produces a single peak
  • Low boiling point (easily removed from sample afterwards)
66
Q

Describe solvents used in 1H NMR

A
  • Must not contain any hydrogens as these would also produce peaks

E.g:
* Tetrachloromethane
* Deuterated solvent (H’s replaced with an isotope of hydrogen, Deuterium)

Chemistry - Mrs McDougal (18 decks)

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