history of synthetic dyes

• birth of chemical and pharmaceutical industries
  • 1856: 1st dye synthesized- mauveine/mauve
  • 1883-1884: direct dyes- 1st class of dyes (for cotton textiles)

• AZO (DOUBLE BONDED NITROGEN)
• AQ SO3H (makes dye water soluble)
• auxochromes (AQ) (NH2 groups)

direct dye features:

• anionic structures, high molecular weight
• contain 1-5 SO3NA/SO3H groups
• display affinity towards cellulose (aka substantive) - attracted towards cellulose
• fixation mechanism- H bonding (hydrogen bonding)
  • van der waals interactions also possible

molecular weight: measure of total weights of all atoms that make up molecule

• express it as grams per mole (g/mol)
• think about a backpack- more items you add, the heavier it is (more atoms you add to molecule, the heavier it is or the higher the molecular weight)

3 examples of direct dye chromophores: