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Chemistry F324 > unit 4 > Flashcards

unit 4 Flashcards

1
Q

Explain the structure of Benzene?

A

There are two ways of representing the structure of benzene.

  • Kekule model ( the pi electrons are isolated in the three double bonds)
  • delocalised model.( The pi electrons are delocalised over the whole benzene structure)

Evidence supports delocalised

  • delta H hydrogenation -208 not -360
  • X rays show bond length the same
  • benzene does not decolourise bromine water. requires catalyst. should go orange to colourless.
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2
Q

Why does benzene take part in substitution reaction?

A

The benzene is fairly stable and substitution reactions allow it to retain its delcalised system and hence its stability.

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3
Q

Decribe the nitration(NO2) of Benzene.

A

Conc HNO3 and Conc H2SO4 added 50 degrees
HNO3+H2SO4===>HSO4- + NO2+ + H20
The NO2 is an electrophile that undergoes electrophilic substitution.

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4
Q

Hescribe the halogenation of benzene?

A

Electrophilic substitution reaction.
Requires: halogen carrier e.g AlCL3 room temp, in the dark.

heterolytic fission of the Cl2 occurs.
Cl2 +AlCL3====>Cl+ + AlCl4-

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5
Q

What is a Halogen carrier?

A

it is an electron defficient molecule that helps produce an electron defficinet halogen atom or alkyl group.

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6
Q

Why can the reaction of Phenol (C6H5OH) be treated in two parts?

A

*The OH group and benzene group react differently, however each one affects the other.

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7
Q

Explain the reactions of the OH group in phenol.

A

*Acts as an acid as it loses a proton, the presence benzene ring weakens the OH bond.

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8
Q

Explain the activation of the benzene rings in phenol.

A

The lone pair of electrons from the oxygen are delocalised on the benzene ring, increasing th electron density in 2,4,6, therefore they decolourise bromine water.

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9
Q

What are some uses for phenols?

A
  • Plastics
  • resins in paint.
  • Antiseptics
  • Disinfectants
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10
Q

What are some uses for esters?

A
  • In perfumes and flavourings
  • Solvent for antibiotics and drugs
  • In biodiesel
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11
Q

Explain Ester hydrolysis?

A

*Acid Hydrolysis
HCL(catalyst) heated under reflux
get OH in the end.

*Alkaline hydrolysis
NaOH heated under reflux
forms OH and O-Na+

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12
Q

What are fatty acids?

A

Fatty acids have a long carbon chain with a carboxylic aci group at the end.

  • no double bond= saturated
  • double bond=unsaturated
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13
Q

How do you name fatty acids?

A

anoic if its unsaturated
enoic if its saturated.

*Shorthand names
N.O of carbon atoms, double bonds(positions of double bonds)

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14
Q

What are trans fatty acids and how do they harm the body?

A

Trans fatty acids are formed from the hydrogenation of vegetable oils, this raises low density lipoproteins, causin risk of obesity coronary heart disease.

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15
Q

What is a tryglyceride?

A

It is a triester of glycerol(propan 1,2,3 triol) and fatty acids.

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16
Q

How do you make bio diesel.

A
  • A process called transesterification
  • Sodium hydroxide catalyst.
  • Tryglyceride + methanon/ethanol ===> biodiesel + glyceride.
17
Q

What is a primary amine?

A

One in which the nitrogen atom is only attached to one carbon chain.

18
Q

How do you name secondary and teriary amines?

A

Secondary has one N in the biginning
tertiary has N,N in the beginning

e.g N,N-diethyl propylamine
N-methyl butylamine

19
Q

Explain the basicity of amines?

A

They are proton acceptors

base+acid===>salt

20
Q

How do you make aromatic arenes?

A
  • Nitrobenzene is reduced to phenylamine and water

* tin and conc HCL heated under reflux

21
Q

State the two steps for the industrial production of dyestuffs.

A

1)Diazotisation
phenylamine, nitrous acid(HNO2) and 2HCL below 10d
* benzene diazonium chloride and water is formed
** HNO2 is formed from NaNO2+HCL.

2) Coupling
* benzene diazonium chloride + phenol + NAOH
* forms the product plus NaCl +H2O

22
Q

What are alpha amino acids?

A

They have both the carboxyl group and basic amine group attached to the same carbon.

23
Q

What is a zwitterion@

A

Dipolar ionic form, formed by the donation of H+ from COOH to NH2

24
Q

How are peptide bonds formed?

A

From condensation reactions water is added.

25
Q

Hydrolysis of polypeptides?

A
  • Acid hysrolysis
  • heated under reflux HCl + water for 24hrs

Alkaline Hydrolysis
*NaOH 100 degrees

26
Q

What are condensation polymers?

A

The joining of two monomers by the removal of a small molecule such as water or HCl

Chemistry F324 (2 decks)

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