I want to show some basic concepts in organic Chemistry using this revision note for organic chemistry class II.
REMEMBER THE FOLLOWING CONVERSIONS
- Hydrogenation of Alkenes yields alkanes
- Polymerization of ethene yields polyethene
- Polymerization of ethyne yields benzene
- Polymerization of benzene yields cyclohexane
- Hydrogenation of vegetable oil yields margarine/butter
- Hydration of alkenes yields alcohols/alkanaols
- Hydrolysis of alkenes yields alcohols/alkanols
- Incomplete oxidation of primary alkanols yields alkanals and complete oxidation yields alkanoic/carboxylic acids
- Oxidation of secondary alkanols yields alkanones
- Oxidation/hydroxylation of alkenes using KMnO4 yields a diol (alkanol)
- Complete combustion of hydrocarbons yields carbon IV oxide and water
- Incomplete combustion of hydrocarbons yields carbon monoxide and water
- Dehydration of Alkanols in excess sulphuric acid yields alkenes
- Dehydration of Alkanols in excess ethanol yields ethers (ROR)
- Dehydration of sucrose/glucose yields soot (carbon)
- Hydrolysis of starch yields glucose
- Hydrolysis of protein yields amino acid
- Bromine water and potassium manganate VI are used to distinguish alkynes/alkenes from alkanes
- 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
- Hydrocarbons: Organic compounds that contain carbon and hydrogen only.
- 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.
- Isomerism: The existence of organic compounds with same molecular formula but different structural formula.
- Octane rating: The grading used in checking the quality of petrol.
- Cracking: This is the breaking down of hydrocarbons like alkanes into smaller hydrocarbons
- Reforming: This is the rearrangement of atoms in a compound to yield a getter quality hydrocarbon.
- Polymerization: This is the coming together of two smaller molecules called monomers to form heavy molecules called polymers.
- Saturated compounds: Saturated compounds are compounds that contain only single bonds.
- Unsaturated compounds: unsaturated compounds are compounds that contain double or triple bond.
SUMMARY OF THE HOMOLOGOUS SERIES AND THEIR FUNCTIONAL GROUPS
|Families of organic compounds||Functional group||General formula|
|Alkanols||Hydroxyl group R-OH||CnH2n+1OH/ROH|
|Alkanoic acid/carboxylic acid||Carboxyl group RCOOH||Cn-1H2n-1COOH/RCOOH|
|Alkanoates /Esters||Ester linkage RCOOR||CnH2n+1COOCnH2n+1/RCOOR|
TESTS FOR SUBSTANCES IN ORGANIC CHEMISTRY
|1||Test to distinguish unsaturated (Alkenes/Alkynes) from saturated (Alkanes||Test: Bromine water |
Result: The unsaturated changes bromine water from orange to colorless
|2||Test for the presence of alcohols||Test 1: Sodium metal Test |
Result : Effervescence of hydrogen indicates alcohol Test
2: Ester Test
Result: Sweet smell indicates alcohol
Test 3: Oxidizing agent (KMnO4/K2Cr2O7)
Result: KMnO4 Changes from purple to colorless K2Cr2O7 Changes from orange to green
Test 4: Ceric Ammonium nitrate Test
Result: A red precipitate shows the presence of alcohol
Test 5: Iodoform Test
Result: A yellow precipitate observed
|3||Test to differentiate the Types of Alcohols||Test: Lucas reagent (HCl/ZnCl) Tertiary alcohols react immediately with Lucas reagent to form a turbid solution|
|4||Test for Fats and oils||Test 1: Paper Test |
Result: A drop of oil forms a translucent grease spot
Test 2: Sudan III test Result; Add 4 or 5 drops of Sudan III test to the oil, the oil is stained red.
|5||Test to distinguish between Alkanals from Alkanones||Test 1: Fehling’s solution |
Result: Add a few drops of Fehling solution and boil, a brick red precipitate observed
Test 2: Tollens reagent
Result: A mirror image of silver formed in the test tube
|6||Test for Glucose||Test 1: Fehling solution |
Result: A brick red precipitate obtained on boiling
Test 2: Benedict’s solution
Result: An orange precipitate shows a positive test
|7.||Test for Protein||Test: Millons Test |
Result: Formation of white precipitate which turns brick red on heating.
Test:Biuret Test Result: Formation of Violet coloration
|8||Test for Starch||Test: Iodine Test solution |
Result:A dark blue/blue-black solution which disappears on heating and appears on cooling
|9||Test for Sucrose||Test: Seliwanoffs test |
Result;A red stain observed
|10||Test for carboxylic acids||Test: Sodium hydrogen carbonate (NaHCO3) test |
Result : evolution of carbon IV oxide gas
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
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.