CHEM BRAINS: TIPS TO IDENTIFY ORGANIC COMPOUNDS

Some Guidelines to Solve Organic Problems

To learn organic chemistry in detail there is no better way than doing lots of problems. Do as many problems as you can, as regularly as you can and shortly you will be able to do them in your head.
After that you will be familiar with the organic chemistry.

The organic problems originate from many sources like books, examinations, one’s own creation, etc.,

Alter the Text question into a Flow chart;
Normally it is good decision to start where much information appears;
Always use Structural formula;
Always count the atoms to avoid a silly mistake;
Do not commit immediately to a conclusion on the structures;
Do not judge the answer until you have solved the problem or until you really have finished all possible trials;

Some of the problems purposely use reactions that are not in the scheme. There is always enough information provided to bring them into the scheme.

Generally Question No. 70(a) and 70(c) is from

a. Hydroxy derivatives linked with Carbonyl compounds and Carboxylic acids.

b. Carbonyl compounds linked with Carboxylic acids and Organic nitrogen compounds.

1. FROM HYDROXY DERIVATIVES

1. Ethyl alcohol –M.F– C₂H₆O [CH₃CH₂ – OH]

Primary alcohol,

Liberates H₂ with Sodium metal,

No turbidity with anhydrous ZnCl₂/Conc.HCl in Lucas test,

gives Red colour in Victor Meyer’s test,

undergoes Iodoform test, etc_.,

2. iso-Propyl alcohol –M.F– C₃H₈O [(CH₃)₂CH – OH]

Secondary alcohol,

Liberates H₂ with Sodium metal,

gives turbidity within 5–10 minutes with anhydrous ZnCl₂/Conc.HCl in Lucas test,

gives Blue colour in Victor Meyer’s test,

undergoes Iodoform test, etc_.,

3. tert-Butyl alcohol –M.F– C₄H₁₀O [(CH₃)₃C – OH]

Tertiary alcohol,

Liberates H₂ with Sodium metal,

isomeric with n-Butyl alcohol and sec-Butyl alcohol,

forms turbidity immediately with anhydrous ZnCl₂/Conc.HCl in Lucas test,

undergoes only dehydration with Cu to give alkene / olefin (Isobutylene),

No reaction with Nitrous acid in Victor Meyer’s test (Colourless solution)_, etc_.,

4. Ethylene glycol–M.F–C₂H₆O₂[OH – CH₂– CH₂– OH]

Dihydric alcohol,

Liberates H₂ with Sodium metal,
with anhydrous ZnCl₂gives Acetaldehyde,
with conc. H₃PO₄ gives Diethylene glycol,
gives Terylene with Terephthalic acid,
with conc H₂SO₄gives Dioxan,
on oxidation with acidified K₂Cr₂O₇ / KMnO₄gives Formic acid,

used as coolant in aeroplane engines, etc_.,

5. Glycerol–M.F–C₃H₈O₃ [OH – CH₂– CH (OH) – CH₂– OH]

Trihydric alcohol,

obtained from soap and candle industry,

used in copying inks and stamp pad inks, etc_.,

6. Benzyl alcohol–M.F–C₇H₈O [C₆H₅– CH₂– OH]

Arylated aliphatic alcohol,

obtained from Cannizzaro reaction,
with CH₃COOH in the presence of conc. H₂SO₄gives Benzyl acetate which has the fragrance of jasmine,

Antiseptic in ointments, etc_.,

7. Phenol –M.F– C₆H₆O [C₆H₅ – OH]

Carbolic acid odour,

prepared from Cumene,
gives violet colour with neutral FeCl₃,

with Bromine water gives white precipitate,

answers Dye test / Coupling reaction,

with CHCl₃ and NaOH gives two isomers – o-Hydroxy benzaldehyde / Salicylaldehyde and p-Hydroxy benzaldehyde (Riemer-Tiemann reaction),

with CCl₄ and NaOH gives two isomers – o-Hydroxy benzoic acid / Salicyclic acid and p-Hydroxy benzoic acid,

with CO₂ and alkali gives o-Hydroxy benzoic acid / Salicylic acid (Kolbe’s reaction),

with HCHO and NaOH it condenses to give p- Hydroxy phenyl methanol,
used to prepare Bakelite, Phenolphthalein, Picric acid, etc.,

2. FROM CARBONYL COMPOUNDS

1. Acetaldehyde–M.F–C₂H₄O [CH₃– CHO]

Undergoes Aldol Condensation,

undergoes Addition reaction with bisulphite, hydrazine, phenyl hydrazine, semicarbazide, hydrogen cyanide, hydroxylamine, etc.,

gives Aldimine on reaction with ammonia,

undergoes Clemmenson reduction with Zinc amalgam and con.HCl,

undergoes Wolf-Kishner reduction with Hydrazine and Sodium ethoxide,

reduces both Tollen’s reagent and Fehling’s solution,

gives pink colour with Schiff’s reagent,

gives Secondary alcohol with Grignard addition,
with Conc.H₂SO₄ undergoes polymerization to give Paraldehyde, a cyclic compound, etc.,

2. Formaldehyde –M.F– CH₂O [HCHO]

Undergoes Cannizzaro reaction,

undergoes Addition reaction with bisulphite, hydrazine, phenyl hydrazine, semicarbazide, hydrogen cyanide, hydroxylamine, etc.,

gives Urotropine on reaction with ammonia,

undergoes Clemmenson reduction with Zinc amalgam and con.HCl,

undergoes Wolf-Kishner reduction with Hydrazine and Sodium ethoxide,

reduces both Tollen’s reagent and Fehling’s solution,

gives Primary alcohol with Grignard addition,

used in biological specimens, etc_.,

3. Acetone–M.F–C₃H₆O [CH₃– CO – CH₃]

Undergoes Aldol Condensation,

undergoes Addition reaction with bisulphite, hydrazine, phenyl hydrazine, semicarbazide, hydrogen cyanide, hydroxylamine, etc.,

gives Diacetone amine on reaction with ammonia,

undergoes Clemmenson reduction with Zinc amalgam and con.HCl,

undergoes Wolf-Kishner reduction with Hydrazine and Sodium ethoxide,

on oxidation gives acid having lesser number of carbon atom compared to acetone,

does not reduce Tollen’s reagent and Fehling’s solution,

answers Iodoform test,

gives Tertiary alcohol with Grignard addition,
with dry HCl gives Mesityl oxide (C₆H₁₀O) and then Phorone (C₉H₁₄O),

in the presence of conc.H₂SO₄ condenses to give Mesitylene / 1, 3, 5-Trimethyl benzene (C₉H₁₂),

used in the manufacture of Cordite,

used in the preparation of Sulphonal, etc.,

4. Benzaldehyde–M.F– C₇H₆O [C₆H₅– CHO]

Has Smell of bitter almond and known as Oil of bitter almonds,

Undergoes Cannizaro reaction,

reduces Tollen’s reagent only,

Does not reduce Fehling’s solution,

gives pink colour with Schiff’s reagent,

undergoes Addition reaction,

gives Hydro benzamide on reaction with ammonia,

undergoes Clemmenson reduction with Zinc amalgam and con.HCl to give Toluene (C₇H₈),

undergoes Wolf-Kishner reduction with Hydrazine and Sodium ethoxide to give Toluene (C₇H₈),

gives Schiff’s base with Pimary amines,

with Aniline gives Benzanilide,

with Cl₂ in the absence of a catalyst gives Benzoyl chloride (C₇H₅OCl),

with Cl₂ in the presence of a catalyst gives m-Chlorobenzaldehyde (C₇H₅OCl),

oxidized by alkaline KMnO₄ to give Benzoic acid(C₇H₆O₂)_,

with aqueous alcoholic KCN gives Benzoin (C₁₄H₁₂O₂) [Benzoin Condensation]_,

with Acetic anhydride in the presence of Sodium acetate gives Cinnamic acid (C₉H₈O₂) which is an aromatic unsaturated acid [Perkin’s reaction]_,etc_.,

5. Salicylaldhyde / o–Hydroxy benzaldehyde –M.F–C₇H₆O₂[o- HO – C₆H₄– CHO]

Obtained from Riemer-Tiemann reaction, etc_.,

6. Acetophenone–M.F– C₈H₈O [C₆H₅– CO – CH₃]

Prepared by Friedel-Craft’s acetylation and Dry distillation of Calcium benzoate and Calcium acetate,
undergoes reduction to give Phenyl methyl carbynol,

undergoes Haloform reaction,
used as hypnotic (Hypnone), etc_.,

7. Benzophenone –M.F– C₁₃H₁₀O [C₆H₅– CO – C₆H₅]

Prepared by Friedel-Craft’s benzoylation and Dry distillation of Calcium benzoate,

undergoes reduction to give Diphenyl carbynol (Benzhydrol),
used in perfumery and preparation of benzhydrol drop, etc_.,

3. FROM CARBOXYLIC ACID

1. Acetic acid –M.F–C₂H₄O₂[CH₃– COOH]

Does not reduce Tollen’s reagent and Fehling’s solution,

gives effervescence with the liberation of CO₂ with carbonates,
gives Ester (Fruity odour) with alcohols, etc_.,

2. Formic acid –M.F–CH₂O₂[HCOOH]

Reduces both Tollen’s reagent and Fehling’s solution, etc_.,

3. Lactic acid –M.F–C₃H₆O₃[CH₃– CH OH– CH₃]

Undergoes Haloform reaction,

gives Pyruvic acid with Fenton’s reagent,
on heating gives Lactide,

used in tanning industry,
Optically active, etc.,

4. Oxalic acid –M.F–C₂H₂O₄[HOOC–COOH]

Dicarboxylic acid,

used for removing ink stains and iron stains, etc_.,

5. Succinic acid / Butanedioic acid –M.F– C₄H₆O₄ [HOOC– CH₂– CH₂– COOH]

Dicarboxylic acid,

used in the manufacture of lacquers and dyes, etc_.,

6. Benzoic acid–M.F– C₇H₆O₂[C₆H₅– COOH]

The simplest of aromatic acids,

Prepared by side chain oxidation of benzene derivatives,
with Soda lime gives benzene,
Undergoes oxidation, reduction_,
_Undergoeselectrophilic substitution at meta-position,
used in urinary antiseptic, etc_.,

7. Salicylic acid / o-Hydroxy benzoic acid–M.F–C₇H₆O₃[o- HO – C₆H₄– COOH]

Obtained from Kolbe’s reaction,

with bromine water gives white precipitate,
gives violet colour with neutral Ferric chloride,
with acetic anhydride gives Aspirin which is used as an analgesic and antipyretic,
with alcohol gives pleasant smelling liquid-Methyl salicylate which is present in Oil of winter green,
used as antiseptic and disinfectant, etc_.,

8. Methylacetate–M.F–C₃H₆O₂[CH₃COOCH₃]

Undergoes Claisen ester condensation, etc.,

9. Acetamide–M.F–C₂H₅NO [CH₃CONH₂]

Undergoes Hoffmann’s reaction,

used in soldering flux and plasticizer in cloth, etc.,

10. Acetyl chloride–M.F–C₂H₃OCl [CH₃COCl]

Undergoes Rosenmund reduction with Pd/BaSO4, etc.,

4. FROM ORGANIC NITROGEN COMPOUNDS

1. Nitrobenzene [C₆H₅– NO₂]

Has Smell of bitter almonds and called as Oil of mirbane,

undergoes reduction,

undergoes electrophilic substitution at meta-position,
used to prepare TNT, etc_.,

2. Aniline –M.F–C₆H₇N [C₆H₅– NH₂]

Has fishy odour,

turns brown on exposure to air,
undergoes Carbylamine reaction,
gives Schiff’s base / Aldimine with aldehydes,
with Benzoyl chloride in the presence of NaOH gives Benzanilide (Schotten- Baumann reaction),
gives Benzene diazonium chloride with Nitrous acid [NaNO₂/ HCl] (Diazotization),
used in Sulpha drugs, etc_.,