Revision Notes For Organic Chemistry Class II

I want to show some basic concepts in organic Chemistry using this revision note for organic chemistry class II.

REMEMBER THE FOLLOWING CONVERSIONS

1. Hydrogenation of Alkenes yields alkanes
2. Polymerization of ethene yields polyethene
3. Polymerization of ethyne yields benzene
4. Polymerization of benzene yields cyclohexane
5. Hydrogenation of vegetable oil yields margarine/butter
6. Hydration of alkenes yields alcohols/alkanaols
7. Hydrolysis of alkenes yields alcohols/alkanols
8. Incomplete oxidation of primary alkanols yields alkanals and complete oxidation yields alkanoic/carboxylic acids
9. Oxidation of secondary alkanols yields alkanones
10. Oxidation/hydroxylation  of alkenes using KMnO₄ yields a diol (alkanol)
11. Complete combustion of hydrocarbons yields carbon IV oxide and water
12.  Incomplete combustion of hydrocarbons yields carbon monoxide and water
13. Dehydration of Alkanols in excess sulphuric acid yields alkenes
14. Dehydration of Alkanols in excess ethanol yields ethers (ROR)
15. Dehydration of sucrose/glucose yields soot (carbon)
16. Hydrolysis of starch yields glucose
17. Hydrolysis of protein yields amino acid
18. Bromine water and potassium manganate VI are used to distinguish alkynes/alkenes from alkanes
19. Ammoniacal solutions of CuCl and AgNO₃ are used to

differentiate terminal alkynes from alkenes

20. The gradual breakdown of starch and carbohydrates into smaller molecules like ethanol is called Fermentation

21.Saponification of fats and oil with caustic alkali  yields soap and glycerol (Propan-1,2,3 triol)

DEFINITIONS OF COMMON TERMS USED IN ORGANIC CHEMISTRY

1. Hydrocarbons: Organic compounds that contain carbon and hydrogen only.
2. Functional group: This is a bond, radical, atom or group of atoms specific to a homologous series and which determines the chemical property of the series.
3. Isomerism: The existence of organic compounds with same molecular formula but different structural formula.
4. Octane rating: The grading used in checking the quality of petrol.
5. Cracking: This is the breaking down of hydrocarbons like alkanes into smaller hydrocarbons
6. Reforming: This is the rearrangement of atoms in a compound to yield a getter quality hydrocarbon.
7. Polymerization: This is the coming together of two smaller molecules called monomers to form heavy molecules called polymers.
8. Saturated compounds: Saturated compounds are compounds that contain only single bonds.
9. Unsaturated compounds: unsaturated compounds are compounds that contain double or triple bond.

SUMMARY OF THE HOMOLOGOUS SERIES AND THEIR FUNCTIONAL GROUPS

TESTS FOR SUBSTANCES IN ORGANIC CHEMISTRY

Test to differentiate two organic substances

1. To differentiate Alkanes from Alkyne/Alkynes

Bromine water test; Alkynes/alkene will decolorise bromine water from orange to colourless

2. To differentiate alkynes from alkenes

Ammoniacal solution of AgNO₃/CuCl: Terminal alkynes will form precipitates of carbides but Alkenes will not react.

3. To differentiate Alkanals(Aldehydes) from Alkanones(Ketones)

Tollens reagent/Fehling solution: Alkanals form silvery mirror image with Tollens reagent and brick red precipitate with Fehling solution

4.To differentiate Alkanols(Alcohols) from Alkanoic acids(carboxylic acids)

NaHCO₃ test: Effervescence occurs when Carboxylic acids react with NaHCO₃ but no effervescence with Alkanol

5. Test to distinguish between reducing sugar and non-reducing sugar

Tollens reagent/Fehling solution: reducing sugar from silvery mirror image with Tollens reagent and brick red precipitate with Fehling solution

6. Test to distinguish between amides and amines

Caustic Soda Test: Amides gives effervescence of ammonia which turns red litmus paper blue

7. Test to distinguish between Aldose and Ketose

Seliwanoffs test: Ketose(Non reducing sugar) will form a red precipitate while aldose (reduce won’t

Fehling solution/Benedicts solution test: Aldose will form a red precipitate while Ketose will not

8. Test to distinguish between glucose and Sucrose

Fehling solution test: Glucose will form a red precipitate while Sucrose will not

Basic organic reactions in Chemistry

1. Substitution reactions

A substitution reaction is a reaction common to saturated hydrocarbons like Alkanes and it involves a direct displacement of an atom or group of atoms by another atom or group.

Alkanes undergo substitution reactions

CH₄ + Cl₂ à CH₃Cl + HCl

C₄H₁₀ + Cl₂ à C₄H₉Cl + HCl

2. Cracking reactions

Cracking is common to Alkanes , Alkanes are cracked to give smaller alkanes and alkenes. The cracking is a reaction specific to saturated hydrocarbons.

Please just remember that in cracking the model could be as follows;

Alkanes à smaller alkane + smaller alkene

Alkanes à smaller alkane + smaller alkene + another smaller alkene

Example

C₈H₁₈ à C₅H₁₂ + C₃H₆

3. Combustion reactions

All hydrocarbons on complete combustion release carbon iv oxide and water while incomplete combustion release Carbon monoxide and water

complete combustion         CH₄ + 2O₂ à CO₂ + 2H₂O

Incomplete combustion     2CH₄ + 3O₂ à 2CO + 4H₂O

4. Addition reactions

Alkenes and alkynes undergo addition reactions since they are unsaturated. Alkenes undergo addition reactions with halogens, hydrogen and oxidizing agents.

Addition reaction involves the direct addition of an attacking reagent across the double or triple bond of an unsaturated compound to form a single product.

Examples are the Addition of hydrogen (hydrogenation)

C₂H₄ + H₂ à C₂H₆

Addition of chlorine

C₂H₄ + Cl₂ à C₂H₄Cl₂

5. Polymerization reaction

The polymerization reaction is a type of reaction in which small molecules called monomers to combine to form large molecules called polymers.

Polymerization reactions are of two types; addition polymerization and condensation polymerization.

Alkenes undergo polymerization to yield polymers.

Polymerization of ethene produces Polyethene

Polymerization of propene produces Polypropene

Polymerization of vinyl chloride (styrene) produces polyvinyl chloride (polysyrene)

Polymerization of Tetraflouroethene produces Polytetraflouroethene

6. Oxidation reactions

Oxidation reaction in Chemistry simply describes a reaction in which oxidation occurs. Alkanols can be oxidized by warming with strong oxidizing agents like acidified potassium hepta oxo dichromate VI solutions.

        Oxidation of primary alcohols produces aldehydes/alkanols

        Oxidation of secondary alcohols produces ketones

7. Reduction reactions

This is a reaction in which a compound is reduced ether by adding of hydrogen or gain of electrons. In organic chemistry reduction is commonly carried out using a strong lithium tetrahydridoaluminate III (LiAlH₄).

          Hydrogen of alkenes to form alkanes is a reduction reaction

          Ketones can be reduced to secondary alcohols

         Aldehydes can be reduced to Primary alcohols

8. Decarboxylation reaction

If a carboxylic acid is heated strongly with soda lime, alkanes will be produced.

CH₃CH₂COOH à C₂H₆ + CO₂

CH₃COOH à CH₄ + CO₂

9. Esterification reaction

What is an Esterification reaction? An esterification reaction is a reaction involving alcohol and a carboxylic acid to form ester and water. Esterification is catalyzed with concentrated sulphuric acid.

Alcohols react reversibly with carboxylic acids to form esters and water.

Examples of the esterification reaction

CH₃CH₂COOH + CH₃OH à CH₃CH₂COOCH₃ + H₂O

CH₃COOH + CH₃CH₂OH à CH₃COOCH₂CH₃ + H₂O

10. Hydration reaction

This is the direct passage of steam over an unsaturated compound to form a product.

For example the hydration of alkene yields alcohol

              Hydration of ethene yields ethanol

              Hydration of propene yields propanol

              Hydration of butane yields butanol

 e.g      C₂H₄ + H₂O  à C₂H₅OH

11. Dehydration reaction

A dehydration reaction is a process of removing water from alcohol in order to form

In a dehydration reaction, alcohol can be dehydrated to remove water and form alkenes.

        C₂H₅OH == C₂H₄    H₂O removed

        C₃H₇OH ==C₃H₆   H₂O removed

12. Fermentation reaction

This is the breakdown of molecules like glucose into smaller molecules like ethanol by the aid of enzymes.

     C₆H₁₂O₆ === 2C₂H₅OH + 2CO₂

13.  Saponification reaction

Saponification is the alkaline hydrolysis of fatty acids with caustic soda to form soaps and glycerol.

   Fatty acids + caustic soda(Alkali) ==== Soaps + glycerol (propan 1,2,3 triol)

14. Hydrolysis reaction

Hydrolysis is the splitting of a bond by the action of water in forming a compound that has OH. We have neutral, alkaline, and acid hydrolysis.

This is a complete list of common organic reactions in organic Chemistry.