Question

salicylic acid experiment

376 Em C Chew B e ttelheim Landesberg 5. Below are structures of common aspirin substitutes. Why do ibuprofen and naproxen not give a positive test with 15 ron (Im chloride? Why does acetaminophen give a positive test? HC CH, CH-CH-CH: CH CH-COOH CH ОН CH-COOH CH 0 CH, Acetaminophen Ibuprofen Naproxen Bottles containing old aspirin tablets often smell of vinegar. The presence of what chemical this smell? How does this chemical form?

Answer 1

Acetaminophen compound has phenolic -OH group. Phenol give coloured complex with neutral ferric chloride solution.

Ibuprofen and Naproxen phenolic -OH group is not present so they are not give positive test with ferric chloride.
III. PHENOLIC (AH OH) GROUP Theory The-OH group attached directly to the ring carbon of an aromatic ring is called phenolic -OH group. Phenols are weakly acidic, therefore they are soluble in NaOH solution but at the same time they are not sufficiently acidic to be soluble is sodium hydrogencarbonate solution. Phenols give coloured complex with neutral ferric chloride solution. For example, phenol gives a complex of violet colour as follows: 6C,H,OH + Feci, →[Fe(C H,0))* + 3HCl + 3H* Violet complex Resorcinol, o-, m-and p-cresol give violet or blue colo 11 catechol gives green colour which rapidly darkens. 1 and 2 do not give characteristics colours, Phenols condense with 1. anhydride in the presence of concentrated H,SO, Phenol condeses to give phenolphthalein which gives a dark pink colour with NaOH solution. This is called phthalein dye test. OH он OH Conc. H.SO, 8.00- NOU Excess Naon apo dio

பயா TUEயசானாபாபாபா Table 8.1 : Colours produced by some other phenolic compounds in phthalein dye teat Compound Colour Compound Catechol Colour Usually blue takes longer time to appear red o-Cresol m-Cresol p-Cresol bluish-purple No colour Resorcinol Green fluorescent colour of fluorescein Material Required According 1 Test tube holder Test tubes to Blue litmus paper Ferric chloride solution Conc. sulphuric acid Sodium hydroxide Phthalic anhydride Organic compound containing phenolic -OH group : One : As per need requirement Procedure A. Ferric chloride test Take 2 mL of aqueous or alcoholic solution of the organic compound in a test tube, add neutral lerric chloride solution dropwise and note the colour change. Appearance of a blue, green, violet or red colour indicates the presence of plienolic -OH group. Sulphuric actd Sodium hydroxde Phthalie anhudride B. Phthalein dye test Take 0.1 g of organic compound and 0.1 g of phthalic anhydride in a clean dry test tube and add 1-2 drops of conc. 11,SO, Heat the test tube for about 1 minute in an oil bath. Cooland pour the reaction mixture carefully into a beaker containing 15 ml of dilute sodium hydroxide solution. Appearance of pink, blue, green, red e, colours indicates the presence of phenolic Oll group in the compound. However, the colour disappears on addition of large excess of sodium hydroxide solution,
Bottles containing old aspirin react with moisture aspirin undergoes decomposition it gives salicylic acid and acetic acid. Acetic acid present in old aspirin bottele it gives veniger smell.
CHEY 요 1 + MY OH + H2O - CH OH Salicylic acid Acetic acid Aspirin Acetylsalicylic acid ASA Figure 3. Aspirin reacts slowly with water to give salicylic acid and acetic acid. The green line shows the ester bond that is broken during the hydrolysis reaction.