Question

1. Why is Para Red (as well as other dyes) colored?

2. Consider the amounts of reactants used in the lab to determine the limiting reagent and theoretical yield of Para Red dye. Show calculations. (If these calculations were detailed in the intro, just direct the grader to the page where they can be found).

3. Why do you have to keep the temperature < 50C when preparing the diazonium salt intermediate?

4. What process is used to dye blue jeans? Show the reaction describing this process.

5. What is an interesting property of a mordant dye? Name a mordant dye and draw its structure.

6. Give two examples of fabric compatible with direct dyes. Explain why they are compatible.

7. Give two examples of fabric that are difficult to dye using direct dyeing process. Draw their structure.

Answer 1

Dyes are organic compounds which are coloured due to the extensive and extended conjugation prevailing in these compounds.
Data Page Dye colouud Jxecuta) thuy absob and in the wibu ougion al the specbum (400-700 nm). b) they possess atleast one chromophore la part in the moule where therungy diffuuna Jadween the two ground and excited state uus mithin the range of musible Espectrum) This chromophone basically us a cohyuq and system with altermateria singu and double bonds. This extended conjugation is responsible for ahi udicunse absorbing light within visible range U c) ak prisena of aurochromis ie auillary quoups wire carboxqui acid, sillfonic acid nitro, amino aconal de suppuments the extent of conjugation and hence was fint uthe colour of dye Pamo oud is also calowed do due do 20 exte un conjugaluonthod edends between napthyl and phenyl vung through diazo quoup Co this whole partis chromophoc) -OH and No camoups which seither inouases e movement ey were enhance O conjugation) 2). Vauns Lave vuquerid (which is watquunm quistion) humiting vuagent which times the formation of product Ubecause it is pusent in tessunamuusht than vuquwud. according to statiomibuy Yield = Observed amount of Para sud calculated amount of Para and 3). Amptest cramped diazomum wall is phenyl diazorum walt ue em " or AYNENCIO. At high temperawu

DOT Page Na gas gets cualved from the system ve hina decomposing che alt - Precis used to dye denims is called denim dyeing. It is coloured wrth idye indica and fasse uued for making jeans us mainly catted collon which is mainly composed of cellulose Indigo do not undergo any chemical Usuaction with Labsie unike other dyes. Instead it gets intervocked with the fabric with through physical bands like hydrogen bond Her varndir Waals forces.