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Chemistry > Organics 3 - Benzene, Amino Acids etc. > Flashcards

Organics 3 - Benzene, Amino Acids etc. Flashcards

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1
Q

Is Benzene Aliphatic or Aromatic

A

Aromatic

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2
Q

Give the formula for Benzene

A

C6H6

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3
Q

Describe the bonding in Benzene

A

Each carbon atom has 3 sigma bonds The fourth valence electron is in a p orbital and is delocalised around the ring Creates a delocalised pi ring system of 6 electrons above and below the ring

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4
Q

What is the bond angle in Benzene

A

120 deg

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5
Q

What are the three pieces of evidence against the Kekule structure

A

1) Does not undergo electrophilic addition e.g. decolourise bromine water 2) It is more thermodynamically stable than expected 3) Bond length is shorter than usual C-C but longer C=C

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6
Q

Describe the differences between Benzene and cyclohexene

A

* Benzene undergoes electrophilic substitution, cyclohexene undergoes electrophilic addition * Benzene has delocalised electrons, cyclohexene has localised electrons * Benzene has lower electron density * Benzene is more stable * Benzene does not react with bromine water, cyclohexene does

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7
Q

Describe the halogenation of Benzene

A

1) Electrophile generated (Cl+/Br+)

Cl2 + AlCl3 -> [AlCl4]- + Cl+

Br2 + FeBr3 -> [FeBr4]- + Br+

2) Mechanism - see photo
3) Regeneration

H+ + [AlCl4]- -> AlCl3 + HCl

H+ + [FeBr4]- -> FeBr3 + HBr

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8
Q

Describe the Acylation of Benzene with halogen alkanes

A

Electrophilic substitution

Friedel Crafts reaction

Generation of electrophile:

CH3Cl + AlCl3 -> [AlCl4]- + +CH3

Mechanism (see photo)

Regeneration

H+ + [AlCl4]- -> AlCl3 + HCl

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9
Q

Describe the acylation of benzene with acyl chlorides

A

Electrophilic substitution

Friedel Crafts reaction

Generation of electrophile:

H3C-COCl + AlCl3 -> [AlCl4]- + H3C-C+=O

Mechanism (see photo)

Regeneration

H+ + [AlCl4]- -> AlCl3 + HCl

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10
Q

Naming substituted benzene compounds

A

When benzene in the main group use ____benzene

When benzene is the side group use phenyl prefix

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11
Q

Why is phenol more easily substituted than benzene

A

The lone pair of electrons of oxygen atom overlaps with delocalised pi system

It is incorporated into the pi system so it is now activated

Electron density of pi system is increased so it can now induce dipoles and attracts electrophiles more

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12
Q

Give the structure of primary, second and tertiary amines

A

Primary: R- N-H

|

H

Secondary: R- N-R

|

H

Tertiary: R- N-R

|

R

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13
Q

Naming Amines

A
  • Use suffix amines
  • If more than one carbon chain

N-(short chain),N-(short chain)(long chain)amine

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14
Q

Describe the melting and boling points of amines

A

Relatively high for primary & secondary amines due to H bonding

Increases with Chain Length

Lower for tertiary amines due to no H bonding

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15
Q

Describe the solubility of amines

A

All small amines are soluble - decreases with chain length

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16
Q

Describe the acidity of amines

A

Weak bases (lone pair on nitrogen atom accepts a proton)

17
Q

Describe the production of aliphatic amines from halogenoalkanes

A

Nucleophilic substitution

Primary Amine

* Use conc. HCl in alcoholic solution

R-X + 2NH3 -> R-NH2 + NH2 + NH4+X-

Secondary amines

* Use primary amines in alcoholic solution

Tertiary amines

* Use secondary amines in alcoholic solution

18
Q

Describe the production of amines from nitriles

A

* Reduction

* Use LiAlH4 OR H2 with Ni/Pt catalyst

R-CN + 4[H] -> R-CH2-NH2

19
Q

Describe the production of phenylamine

A

* Reduction of nitrobenzene

* conc. HCl and Sn catalysts

20
Q

Describe and explain the relative base strength of amines

A

Primary Amines > Ammonia > Phenylamine

Primary amines are stronger because the alkyl groups have inductive effect increasing electron density on the nitrogen atom

Ammonia does not have an inductive effect as there are no alkyl groups

Phenylamine is weaker because the lone of pair electrons from the Nitrogen atom are drawn into the delocalised pi system

21
Q

Describe the reaction of amines with water and acid

A

Amines are weak bases

Dissociate in water to produce OH- ions

React with acid to form salts

Salts are named (carbon chain)ammonium(chloride/sulfate/nitrate)

22
Q

Describe the reaction between amines and copper complexes

A

Cu2+ exists as [Cu(H2O)6]2+ (light blue solution)

Add a little butylamine

[Cu(H2O)6]2+ + 2C4H9NH2 <=> [Cu(OH)2(H2O)4] + 2C4H9NH3+

[Cu(OH)2(H2O)4] is a light blue precipitate

Add excess butylamine

[Cu(H2O)6]2+ + 4C4H9NH2 <=> [Cu(C4H9NH2)2(H2O)2]2+ + 4H2O

Dark blue solution

23
Q

Give the general formula for amino acids

A

R

|

H2N- C -COOH

|

H

24
Q

Do amino acids display optical isomerism

A

All but glycine

25
Q

Why do amino acids form Zwitterions

A

The H from the COOH group is donated and is accepted by N in the NH2 group

26
Q

Describe the physical properties of amino acids

A

Very soluble due to zwitterions (two oppositely charged poles)

Very high melting/boiling points due to electrostatic attraction

27
Q

Describe the polymerisation of amino acids

A

Condensation Polymerisation

NH2 and COOH groups react to form amide linkages/peptide bonds

Produces dipeptides

When there are two or more different amino acids joining together there are different possible products (see photo)

28
Q

Describe polypeptides

A

Multiple amino acids come together to form long chains

Primary structure of proteins

29
Q

Describe the acid and alkaline hydrolysis of amino acids

A

Breaks apart peptide bonds

Acid Hydrolysis

NH2 group is protonated to NH3+

Alkaline Hydrolysis

COOH group becomes COO-

Amino acids produced from this can be separated by chromatography

30
Q

Describe Amino Acids in different pHs

A

Le Chatlelier’s Principle

NH2 + H+ <=> NH3+

COOH <=> COO- + H+

In Acidic conditions [H+] increased so NH3+ formed

In alkali conditions [H+] decreased so COO- formed

If R group contains COOH or NH2 groups then they’ll also be affected

31
Q

Describe the formation of Polyamides

A

Condensation polymerisation

Two different monomers used:

  • Dicarboxylic Acids
  • Diamines

350 degrees

Alternatively diacyl chlorides can be used at room temp

32
Q

Describe the structure of proteins

A

Proteins are made up of amino acids chains (polypeptides)

First Level Structure

  • Amino Acid Chains with Amide/Peptide bonds

Second Level Structure

  • Folding of amino acid chains
  • H bonding between amide/peptide bonds

Third Level Structure

  • Further folding
  • Ionic bonds or disulfide covalent bridges in R group

Fourth level structure

Multiple amino acid chains

Possibly a prosthetic group

Chemistry (6 decks)

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