Reactions of organic molecules wace

Question 1

What is produced through the oxidation of different alcohols with acidified potassium dichromate/permanganate

Answer 1

primary: easily oxidised to aldehydes and then to carboxylic acid
secondary: easily oxidised to ketones
tertiary: not oxidised under standard conditions

Question 2

Describe the oxidation of primary alcohols into aldehydes

Answer 2

Aldehydes have low BP (no Hbonds)-distill off immediately when prepared by reaction w/primary
-no distill=oxidised to equivalent carbox. acid
ox: C3H7OH(aq) –>C3H6O(aq) + 2H(aq)+ + 2e-
red: MnO- (aq)+ 8H+(aq) + 5e- –> Mn2+(aq) + 4H2O(l)
overall: 5C3H7OH(aq) + 2MnO- (aq)+ 6H+(aq)–>C3H6O(aq) + 8H2O(aq) + 2Mn2+(aq)

Question 3

Describe the oxidation of primary alcohols into carboxylic acids

Answer 3

To oxidise alcohol straight to acid reflux mixture
ox: C3H5OH(aq) + H2O(l)–>CH3COOH(aq) + 4H+(aq) + 4e-
red: CrO72-(aq) + 14H+(aq) + 6e- –> 2Cr3+(aq) + 7H2O(l)
overall: 3C3H5OH(aq) + 2CrO72-(aq) + 16H+(aq) –> 3CH3COOH(aq) + 4Cr3+(aq) + 11H2O(l)

Question 4

Describe the combustion of alkanes. What causes/comes to be as a result of complete and incomplete?

Answer 4

Alkanes=useful fuels that react with oxygen in exothermic reaction
complete: CH4+2O2–>CO2+2H2O
incomplete: 2CH4+3O2–>2CO+4H2O

-increased number of carbon atoms=more energy produced but increased amount of oxygen needed for completion
-more energy produced by increased carbon atom because more energy released through breaking/making bonds

Question 5

Describe the reagents, conditions and mixtures of substitution reactions

Study over example equation

Answer 5

reagents: halogens (F2, Cl2, Br2, I2)
conditions: UV light (acts as catalyst) or sunlight-heat as alternative energy source
mixtures: Free radicals produced=very reactive as they try to pair their electrons. W/sufficient halogens, every hydrogen will eventually be replaced.

e.g. CH4+Cl2–>CH3Cl+HCl
1:1 reactant ratio
if excess halogens;
CH4+4Cl2–>CCl4+4HCl

Question 6

Describe the reagents, conditions and mixtures of halogenation (addition) reactions

Answer 6

Reagents: halogens
Products: Dihalogenoalkane
Conditions: Room temp
Equation: C2H4(g)+Br2(l)–>CH2BrCH2Br(l)

Question 7

Describe the reagents, conditions and mixtures of hydrogenation (addition) reactions

Answer 7

Reagents: hydrogen
Products: Alkanes
Conditions: Nickel catalyst-finely divided (metal catalyst)
Equation: C2H4(g)+H2(g)–>C2H6(g)

Question 8

Describe the reagents, conditions and mixtures of hydrogen halides (addition) reactions

Answer 8

Reagents: hydrogen halides ( HF, HCl, HBr, HI)
Products: Halogenoalkelane/halogenoalkane
Conditions: Room temp
Equation: C2H4(g)+HBr(g)–>C2H5Br(l)

Question 9

Describe the reagents, conditions and mixtures of hydration (addition) reactions

Answer 9

Reagents: Steam
Products: Alcohol
Conditions: Heat, high pressure, concentrated acid catalyst
Equation: C2H4(g)+H2O(g)–>C2H5OH(g)

Question 10

Describe the oxidation of secondary alcohols into ketones

Answer 10

Easily oxidised into ketones with potassium dichromate/permanganate
ox: CH3CHOHCH3(aq) –> CH3COCH3 + 2H+ + 2e-
red: CrO72-(aq) + 14H+(aq) + 6e- –> 2Cr3+(aq) + 7H2O(l)
overall: 3CH3CHOHCH3(aq) + CrO72-(aq) + 8H+(aq) –> 3CH3COCH3(aq) + 2Cr3+(aq) + 7H2O(l)

Question 11

Describe the oxidation of tertiary alcohols

Answer 11

Cannot oxidise. To oxidise, C atoms carrying hydrogen group must have hydrogen attached to allow for double bond. Have not H attached on tertiary.