Dyes classification

introduction. methyl orange,nitrodye and application

1. 1 Mr.M.RAGU Assistant Professor of Chemistry Vivekananda College Tiruvedakam West – 625234 Madurai - Tamilnadu Classification and Synthesis of Dyes

2. Introduction Theory of color and constitution Chromophore and Auxochrome Nitro dyes and Naphthol yellow Azo dyes Methyl orange T-Chloramine Outline Outline

3. THEORY OF COLOR AND CONSTITUTION CHROMOPHORE A   chromophore  is the part of a  molecule  responsible for its  color It arises when a molecule  absorbs  certain  wavelengths  of  visible light  and transmits or reflects others The energy difference between two different  molecular orbitals  falls within the range of the visible spectrum . Visible light that hits the chromophore can thus be absorbed by exciting an  electron  from its  ground state  into an  excited state . White light is a continuum of different colours. If white light is passed through clouds or a prism, then it can be split up into its constituent colours, each of which has a different wavelength.

4. Examples of Chromophores If there is only conjugation, a long chain of conjugated bonds is needed to reduce the HOMO/LUMO gap to energies that correspond to visible light. Realize that it is continuous, extended conjugation that is important (i.e. the size of the molecular orbital), not the total number of double bonds. If we continue to increase the number of conjugated C=C bonds, then eventually we reach a point where the compound will absorb visible light (β-carotene ~475 nm). Keto group, Nitroso group, Quinonoid group, Ethylenic group, Nitro group, azo group.

5. Chemical structure of  beta-carotene . The eleven conjugated double bonds that form the chromophore of the molecule are highlighted in red An  auxochrome  (Gr.  Auxanein : to increase,  chroma :colour ) is a group of atoms attached to a  chromophore   They themselves fail to produce the colour; but when present along with the chromophores increase in color Acidic :  -COOH , -OH,  - SO 3 H ; Basic : -NHR, -NR 2 , -NH 2 AUXOCHROME 

6. NITRO DYES a  group  of dyes; aromatic compounds whose  color  results from the presence of nitro groups, NO 2 , and  hydroxyl  and  iminogroups , OH and NHR (R is an alkyl or aryl group).  They  may also contain  Cl , SO 3 H, and COOH  substituent's. Nitro dyes containing  imino  groups  are  more stable . It is produced by the reaction of 2,4-dinitrochlorobenzene with p-aminophenol.

7. NAPHTHOL YELLOW I t  is  used  in a number of countries as a food dye .  It is produced by  sulfonation  of α- naphthol ,  with subsequent  nitration of the product. Nitro dyes (for example, picric acid) were among the first industrial dyes. They lost their practical importance as a result  oftheir  low  stability.

8. AZO DYES

9. It  is a  pH indicator  frequently used in  titrations  because of its clear and distinct colour change . Its not an universal indicator   Colourless solid is soluble in nonpolar organic solvents and not in water. METHYL ORANGE

10. It can be synthesized by  Friedel -Crafts reaction  from  benzene  and  chloroform  with  aluminium chloride catalyst : 3 C 6 H 6  + CHCl 3  → Ph 3 CH + 3 HCl TRIPHENYLMETHANE DYES Basic skeleton of many synthetic  dyes called  triarylmethane dyes

11. Examples of triarylmethane dyes are  bromocresol green : ii) Benzene may react with  carbon tetrachloride  using the same catalyst to obtain the  trityl chloride - aluminium chloride  adduct, which is hydrolyzed with dilute acid: 3 C 6 H 6  + CCl 4  + AlCl 3  → Ph 3 CCl·AlCl 3 Ph 3 CCl·AlCl 3  + HCl → Ph 3 CH

12. It is prepared by   condensing   benzaldehyde  and  dimethylaniline  in the molecular ratio 1:2 in the presence of  sulfuric acid MALACHITE GREEN DYES

13. N - phenylglycine is treated with a molten mixture of  sodium hydroxide ,  potassium hydroxide , and  sodamide . This highly sensitive melt produces  indoxyl , which is subsequently oxidized in air to form indigo. INDIGO DYES

14. Alizarin is one of ten  dihydroxyanthraquinone  isomers. Its molecular structure can be viewed as being derived from anthraquinone  by replacement of two  neighboring   hydrogen  atoms (H) by  hydroxyl  groups (-OH ). It is soluble in hexane and chloroform ANTHRAQUINONE DYES

15. Derivatives of 9,10-anthraquinone include many important drugs (collectively called  anthracenediones ). Antimalarials  such as  rufigallol Antineoplastics  used in the treatment of  cancer , such as  mitoxantrone ,  pixantrone Aloe emodin   mitoxantrone pixantrone

16. It can be prepared from  phthalic anhydride  and  resorcinol  in the presence of  zinc chloride  via the Friedel -Crafts reaction . FLUORESCEIN DYES

17. It is an  organosulfur compound  with the formula  C 6 H 5 S O 3 H . It is the simplest  aromatic   sulfonic acid . It is often stored in the form of  alkali metal salts . Its aqueous solution is  strongly acidic Preparation Benzenesulfonic acid is prepared from the   sulfonation  of  benzene  using concentrated  sulfuric acid BENZENESULFONIC ACID

18. of other aromatic  sulfonic acids , forming sulfonamides , sulfonyl chloride, and esters. The sulfonation is reversed above 220 °C. Dehydration with  phosphorus pentoxide  gives benzenesulfonic   acid anhydride  ((C 6 H 5 SO 2 ) 2 O). Conversion to the corresponding benzenesulfonyl chloride (C 6 H 5 SO 2 Cl) is effected with  phosphorus pentachloride . It is a strong acid, being dissociated in water. The alkali metal salt of benzenesulfonic acid was once widely used in the production of  phenol : C 6 H 5 SO 3 Na + 2 NaOH → C 6 H 5 ONa + Na 2 SO 3 C 6 H 5 ONa + HCl → C 6 H 5 OH + NaCl

19. It  is an  artificial sweetener  with effectively no  food energy  which is about 300–400 times as sweet as sucrose. It starts with  toluene ; Sulfonation by  chlorosulfonic acid  gives the  ortho  and  para  substituted  sulfonyl chlorides . The  ortho  isomer is separated and converted to the  sulfonamide   with ammonia . Oxidation of the methyl substituent gives the carboxylic acid, which cyclicizes to give saccharin free acid SACCHARIN

20. Anthranilic acid  successively reacts with nitrous acid  (from  sodium nitrite  and  hydrochloric acid ),  sulfur dioxide ,  chlorine , and then  ammonia  to yield saccharin

21. CHLORAMINE-T Chloramine -T is slightly basic (pH typically 8.5). In water, it breaks down to the disinfectant  hypochlorite . It can be used as a source of electrophilic chlorine in  organic synthesis . Chloramine -T is prepared from  p - toluenesulfonamide and sodium hypochlorite, with the latter being produced  in situ from   sodium hydroxide  and chlorine (Cl 2 )

22. Applications It is widely used for the incorporation of iodine to peptides and proteins. Chloramine -T together with  iodogen  or  lactoperoxidase  is commonly used for  labeling  peptides and proteins with radioiodine  isotopes  Chloramine -T is available in tablet or powder form and has to be dissolved before use. The substance is also used for  parasite control and for drinking water disinfection. It reacts readily with  mustard gas  to yield a harmless crystalline  sulfimide ; chloramine -T derivatives are being studied as protective agents against poison gas

23. SULFONAMIDE  OR  SULPHONAMIDE   It is the basis of several groups of drugs. The original antibacterial sulfonamides (sometimes called  sulfa drugs  or  sulpha drugs ) are synthetic antimicrobial agents that contain the  sulfonamide  group. Some sulfonamides are also devoid of antibacterial activity Sulfonamides are prepared by the reaction of a  sulfonyl chloride  with ammonia or an amine. Hydrochlorothiazide Furosemide

24. 27 Mr.M.RAGU Assistant Professor of Chemistry Vivekananda College Tiruvedakam West – 625234 Madurai - Tamilnadu Thank you