Starter - complete the following scheme giving Starter - complete the following scheme giving all Formulaall Formula

Ethyl ethanoate

Formula?

Ethanoyl chloride

Formula?

Ethanoic acid

CH3COOH

CH3COCl

CH3COOC2H5

Reagents?C2H5OH

C2H5OH

+ Conc H2SO4

Reagents?

H+ CH3COOH + C2H5OH

OH-

C2H5NH2 /

ethanol

salt + ethanol

CH3COO- + C2H5OH

ethanamide

CH3CONH2

NH3 / ethanol

N-ethylethanamide

CH3CONH2C2H5

Reactions of Amides

How can you make ethanamide?

1. ethanoyl chloride and

O

NH2

CCH3

O

+ NH4Cl CCH3

Cl

+ NH3

ethanoyl chloride + ammonia ethanamide + ammonium chloride

ammonia

Reactions of amides

1. draw the full structural formula for ethanamide and H3O+

O

NH2

CCH3 + H3O+

O

OH CCH3 + NH4

+

ethanamide + acid organic acid + ammonium ion

Reactions of amides

2. Basic conditions

O

NH2

CCH3 + OH-

O

O- CCH3 + NH3

ethanamide + base conjugate base + ammonia of acid

Synthetic polymers

Polyamides

Polyamides can be made by combining a ________ and a _____________acid

Nylon 6,6 can be made into fibres to make pantyhose or in other forms gear wheels with tough properties

Nylon 6,6 is made from _____________ acid and

_________________ Draw the structural formula of these two compounds

C

HO

O

CH2CH2CH2CH2C

O

OH

hexanedioic acid

H

H

N CH2CH2(CH2)4 N H

H

1,6 diaminohexane

diaminedicarboxylic

hexanedioic

1,6 diaminohexane

Synthetic polymers continued

Polyamides

Nylon 6,6 is an example of a ____________ polymer

C

HO

O

CH2CH2CH2CH2C

O

OH

hexanedioic acid

H

H

N CH2CH2(CH2)3CH2 N

H

H

1,6 diaminohexane

C

HO

O

CH2CH2CH2CH2C

O

Water removed means a condensation reaction

Peptide link

condensation

Draw the structural formula of nylon 6,6

Task – write the balanced redox reactions for the oxidation of the oxidation of propan-1-ol to propanal using Cr207

2- /H+ and give all colour changes.

CH3CH2CH2OH

Cr2072-

CH3CH2COH + 2H+

+ 2e-

2Cr3+

+ 7H20

+ 14H+

+ 6e-

(X3) 3

3

+ 6H+

+ 6e-

3CH3CH2CH2OH + Cr2072- + 2Cr3+

+ 7H20

+ 8H+

3CH3CH2COH

Full balanced redox equation

The Lucas TestThe Lucas TestWhat is the lucas test?

The Lucas test is used to distinguish between the 3 types of alcohols

The Lucas reagent consists of ZnCl2 in concentrated HCl

The zinc chloride catalyses a substitution reaction between the alcohol and the concentrated HCl

Chloroalkanes form and appear as a cloudy suspension in the water because they are insoluble. 3o then 2o then 1o

What reagents does the lucas test consist of?

What do you observe ocurring with a positive lucas test?

What is the purpose of the zinc chloride and what kind of reaction occurs

Task – write the balanced redox reactions for the oxidation of the oxidation of propan-2-ol to propanone using Mn04

- /H+ and give all colour changes.

CH3CHOHCH3

Mn04-

CH3COCH3 + 2H+

+ 2e-

Mn2+

+ 4H20

+ 8H+ + 5e-

(X5) 5

5

+ 10H+

+ 10e-

5CH3CHOHCH3 + 2Mn04- +

2Mn2+ +8H20 +

6H+ 5CH3COCH3

Full balanced redox equation

(X2)

2MnO4-

+ 16H+ + 10e- +

8H20 2Mn2+

REDOX 90696 2005 QUESTION ONE: COBALT AND CHROMIUM IN REDOX REACTIONS

An electrochemical cell is set up using appropriate electrodes and solutions of potassium dichromate and cobalt(II) nitrate. It is based on the following half-cell reactions: 

Co2+ + 2e– Co E° = – 0.28 V

Cr2O72– + 14H+ + 6e– 2Cr3+ + 7H2OE° = +1.36 V

 

(a) Write a balanced equation for the spontaneous reaction that would occur in the cell.(b) Calculate the E° for the spontaneous reaction in the above cell.(c) Complete the diagram below to show how the electrochemical cell would be set up. On your diagram label the electrodes, the solutions (electrolytes) and indicate the direction of the flow of charge (cations, anions and electrons) between the two half-cells.

3Co + Cr2O72– + 14H+ → 2Cr3+ + 7H2O + 3Co2+ Correct equation.

2005 1a. Achieved

Eo cell = E(Cr2O72– /Cr3+ ) – E(Co2+ / Co)

= +1.64 V Correct answer.

1b. Achieved

Salt bridge drawn connecting half-cells. One half-cell: Co electrode, Co2+

solution Other half-cell: Inert electrode eg Pt electrode, K2Cr2O7 Achieved - Salt bridge shown OR ONE half cell correctly labelled.

Merit - ALL aspects of the cell correctly drawn and labelled.

1c. Pt 1 Evidence

• e – flow from anode to cathode (Co to Pt)• anion movement toward anode (Co)• cation movement toward cathode (Pt)Achieved - Correct direction for electrons OR one of the ions.Merit - ALL movement of charge correct.

1c. Pt 2 Evidence

2005 1(d) Complete the standard cell diagram for this cell. 

 

(e) Cobalt is a transition metal that exists in both the +2 and +3 oxidation states.  A piece of cobalt metal is reacted with acidified potassium dichromate solution. Using the relevant reduction potentials, determine if the cobalt ion produced in this reaction is Co2+ or Co3+. E°(Co3+/Co2+) = +1.82 V

From 1 (a) spontaneous reaction produces Co2+ E° for reaction between Co2+ and Cr2O7 2– 1.36 –1.82 < 0 V. Hence reaction for further oxidation is not spontaneous so oxidation to Co2+

not Co3+.

Achieved Co│Co2+ ║Cr2O7 2–, Cr3+ │Pt

Any inert electrode acceptable. States maybe included.

Achieved Correct reactionrecognised either by theactual reaction OR byinference using the Eovalues OR by saying Co2+

formed.

Merit Correct answer withpartial explanation thatincludes calculations andcomments on thefeasibility, and alsoidentifies that Co2+ isformed.

ExcellenceCorrect answer withfull explanation.May approach fromthe reverse direction.

Reactions of Acid Chlorides2. Forming esters from acid chloride – reagents are a primary alcohol

O

O C R

R’

From acyl chloride

From alcohol

+ HCl

CH3COCl + CH3OH CH3COOCH3 + HClethanoyl chloride + methanol methyl ethanoate + hydrogen chloride

Ester

Reactions of Acyl Chlorides

3. acyl chlorides form amides – reagent ammonia and heat

O

NH2

C RFunctional group of the amide

CH3COCl + 2NH3 CH3CONH2 + NH4Clethanoyl chloride + ammonia ethanamide + ammonium

chloride

4. Acyl chlorides forming N - substituted amides – reagent amine O

NH C R N substituted amide

Reactions of Acyl Chlorides

R’

O

Cl C CH3 + NH2 CH3

O C CH3 +

HClCH3NH

Ethanoyl chloride + aminomethane N – methyl ethanamide

+ hydrochloric acid

Acyl chlorides react with water to form acidic solutions

Reactions of Acyl Chlorides

O

Cl C CH3 H

HO

O C CH3

HO+ HCl

ethanoyl chloride + water ethanoic acid + hydrogen chloride