(Write in LHS) Experiment 5 PREPARATION OF 2-NAPHTHOL ANILINE DYE
Chemical reaction
- 2- naphthol aniline dye is a scarlet dye. It belongs to the class of azo compounds which are all coloured. It involves diazotisation and coupling reactions.
(Write in RHS ) Experiment 5 PREPARATION OF 2-NAPHTHOL ANILINE DYE Date:
AIM –
To prepare 2- naphthol aniline dye
THEORY - 2- naphthol aniline dye is a scarlet dye. It belongs to the class of azo compounds which are all coloured. It involves diazotisation and coupling reactions.
APPARATUS AND CHEMICALS
250ml Conical flask, 250ml ml beaker, 100ml beaker, ice bath, glass rod, Funnel, filterpaper, distilled water, a) Aniline 2.25g b) sodium nitrite 2g
c)2 naphthol 3.5g d) Conc. HCl 5ml e)Glacial acetic acid 20ml
PROCEDURE
Take 250ml Conical flask, 250ml ml beaker, 100ml beaker.
In 250ml conical flask add 2.25ml aniline, dissolve about 0.1g of the compound in 5ml of concentrated hydrochloric acid. Cool the solution to 50C by placing the conical flask in a trough containing ice cold water.
In 100ml beaker dissolve 2g of sodium nitrite in 10ml of distilled water and cool this solution also to 50C
Now slowly add sodium nitrite solution to the solution of aniline in conc. HCl
Dissolve 3.5g of 2- naphthol in 30ml of 10% NaOH solution taken in s 250ml beaker and cool this solution to 50C by placing in an ice bath. Some rushed ice may be added directly to fecilitate cooling.
Now add the diazotised solution very slowly to the naphthol solution with constant stirring. The mixed solution immediately develop a deep red colour and the benzene azo naphthol rapidly separates as red crystals
When addition of diazo solution is complete, allow the mixture to stand in ice salt mixture for 30 minutes, with occasional stirring. Filter the solution. Dry the crystals by placing it over filter paper.
Recrystallise using glacial acetic acid.
Deep red crystals of 2- naphthol aniline dye (approximate weight 1.5g) with melting point 1330C obtained.
RESULT
2-NAPHTHOL ANILINE DYE PREPARED
PRECAUTIONS
1. The solution of the aniline hydrochloride should be cooled to 50C, and this temperature maintained throughout the addition of the sodium nitrite solution
2. Addition of sodium nitrite should be very slow because the reaction is exothermic and may cause the temperature to rise.
