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1. introduction to preparation and structure of some common dyestuffs


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introduction to preparation and structure of some common dyestuffs

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1. introduction to preparation and structure of some common dyestuffs

  2. 2. Dyes are colored organic compounds that are used to impart color to various substrates, including Paper Leather Hair Drugs Cosmetics Waxes Greases Plastics and Textile materials
  3. 3. Dyes may be classified according to their chemical structure or by the method by which they are applied to the substrate. The dye manufacturers and dye chemists prefer the former approach of classifying dyes according to chemical type. The dye users, however, prefer the latter approach to of classification according to application method. Classification by application or usage is the principal system adopted by the Color Index (C.I.).
  4. 4. Azoic Dyes Acid Dyes Basic (Cationic) Dyes Direct Dyes Disperse Dyes Reactive Dyes Mordant Dyes Sulfur Dyes Vat Dyes
  5. 5. 1.1 Azo Dyes Are:-  Larger groups  N=N  NH2, NR2, OH There may be more than one azo group  Mono, Di, Tri, Tetrakis and poly Prepared by Diazotization of primary aromatic amines= Diazonium salt/diazo and then coupled with phenol or amine
  6. 6. Diazotization When aromatic amine is added on aqueous acid medium by nitrous acid a diazonium salt is formed and the amine is said to be has been diazotized. Rate determining step-nitration of amine Ar. = aromatic hydrocarbon radical
  7. 7. Diazo CouplingDiazo Coupling  Electrophilic substitution by diazonium salt.Electrophilic substitution by diazonium salt.  Comparing withComparing with ++ NONO22 and SOand SO33 -- thethe diazoniumdiazonium cation is a weak electrophile and powerfulcation is a weak electrophile and powerful electron donating groups such as -OH, -NH2,electron donating groups such as -OH, -NH2, -NR2 must be present in the aromatic system of-NR2 must be present in the aromatic system of the coupling component for coupling to take place.the coupling component for coupling to take place. Coupling Components areCoupling Components are  Benzene Derivatives like amines at acidicBenzene Derivatives like amines at acidic mediummedium  Hydroxyl derivatives at alkaline mediumHydroxyl derivatives at alkaline medium  Salicylic Acid at alkaline mediumSalicylic Acid at alkaline medium  Naphthalene Derivatives at alkaline mediumNaphthalene Derivatives at alkaline medium
  8. 8. Examples of Diazotization and coupling on fiber
  9. 9. 1.2 Cationic Dyes( Mono Azo)  Usually hydrochlorides of bases having moderate solubility in water  Drawing chiefly on Azo, Anthraquinone and Triarylmethane and are now commercially available. water-soluble and produce colored cations in solution. mostly amino and substituted amino compounds soluble in acid and made insoluble by the solution being made basic. attached to the fibers by formation of salt linkages (ionic bonds) with anionic groups in the fiber. used to dye paper, polyacrylonitrile, modified nylons, and modified polyesters.
  10. 10. 1.3 Reactive dye Main chromophores employed in this are Azo, Metal Azo, Anthraquinone and Phthalocyanin containing the groups which can react directly with the fiber react with the cellulose fiber to form a covalent bond. This produces dyed fiber with extremely high wash fastness properties. Cotton, rayon, and some nylons are dyed by this relatively simple dye.
  11. 11. Reactive Azo DyesReactive Azo Dyes
  12. 12. 1.4 Vat Dyes Commercial name  Indathrene  Cibanone  Caledon Divided into  Dyes derived from Indigo: Include natural and synthetic indigos and its Bromide and Thioindigo  Dyes Derived from Anthraquinone insoluble complex polycyclic reduced with sodium hydrosulfite in a strongly alkaline medium to give soluble leuco forms that have a great affinity for cellulose. After the reduced dye has been absorbed on the fiber, the leuco forms are reoxidized to the insoluble keto forms.
  13. 13. Synthesis Heumann Process + heat + KOH and NANH2
  14. 14. Sadamine Process Alinine + heat + CS2= Thiocarbonilide + heat + Lead carbonate + NaCN, S = Cyano compound structure + Sodium Hydrosulphide =thioisatin + Alkali=Indigo
  15. 15. 1.5 Disperse Dyes1.5 Disperse Dyes Mono azo, Diazo,Mono azo, Diazo, Anthraquinone, Methine,Anthraquinone, Methine, Quinoline, Nitro,Quinoline, Nitro, AroylenebenzimidazoleAroylenebenzimidazole substantially water-insoluble nonionic application to synthetic hydrophobic fibers from aqueous dispersions. primarily used for polyester and acetate fibers.
  16. 16. Presence of halogens, NO2,Presence of halogens, NO2, CN or electron- withdrawingCN or electron- withdrawing groups in the Diazogroups in the Diazo component causes a shift ofcomponent causes a shift of λλmaxmax to wards the longerto wards the longer wavelengthwavelength bathometricbathometric effecteffect..