Aldehydes, Ketones and Saccharides

Aldehydes – contains a carbonyl group at the end of the carbon chain.
– RCOH

Ketones – contains a carbonyl group in the middle of the carbon chain.
– RCOR

* 2,4-dinitrophenylhydrazine Test – Test for Carbonyl group
* Sodium Bisulfate Test- Test for Aldehydes and Methy Ketones
* White precipitate
* Ketones with more than 2 carbon – non-reactive
* Ketones with 2 carbons – slightly reactive

* Schiff’s Test – Test for aldehydes
* Purple solution
* Formalin – positive
* Acetone (ketone)
* Benzaldehyde – positive
* Acetophenone (aromatic ketone)

* Tollen’s Test – Test for aliphatic and aromatic aldehydes
* Silver mirror
* Formalin – positive
* Glucose – positive
* Benzaldehyde – positive
* Acetone

* Fehling’s Test – Test for Aliphatic aldehydes
* Brick red precipitate (cuprous oxide)
* Formalin – positive
* Glucose – positive
* Benzaldehyde
* Acetone

* Sodium Nitroprusside Test – Test for presence of acetone
* -Wine red solution

* Iodoform Test – Test for Methyl Ketones
* Acetone – positive
* Ethyl methyl ketone – positive
* Ethyl acetate

* Special test for Benzaldehyde
* Formation of crystals

* Molisch Test – General test for Carbohydrates
* Violet ring (2nd layer)
* Glucose – positive
* Starch – positive
* Benzaldehyde

* Bial’s Orcinol Test – Test for Carbohydrates
* 5 carbon – blue to green
* Ribose – green
* 6 carbon – brown
* Glucose – brown

* Phenylhydrazine Test – Test for reducing sugars
* Osazone crystals
* Glucose – positive

* Optical rotation – property of a substance that could rotate the plane of polarization of a beam of polarized light.

Carboxylic acid – RCOOH
– React with strong bases (NaOH, KOH) to form water soluble salts.

* Test for carboxylic acid
* Acetic acid – soluble in water and NaOH
* Stearic acid – insoluble in water and NaOH

* Reaction with sodium carbonate
* Effervescence – release of carbon dioxide

* Esterification
* Acetic acid + n-propyl alcohol → propyl acetate
* Benzoic acid + n-propyl alcohol → propyl benzoate

* Reaction with Neutral FeCl3
* Acetic acid – red-orange precipitate
* Tartaric acid – effluence of red-orange precipitate

* Special Test for tartaric and citric acid
* Citric acid – green solution → colorless solution
* Tartaric acid – brown solution → colorless solution

* Hydroxamic test for esters
* Magenta or burgundy solution

* Hydrolysis reactions
* Acetic anhydride – blue litmus paper → red litmus paper
*Acetamide – red litmus paper → blue litmus paper