CHM 585

1
CHM 585

• Chapter 18
• Dyes and Pigments

2
Dyes

• General
• Azo
• Anthraquinone
• Indigo
• Phthalocyanine

3
Dyes 5 billion world market

• Dyes are intensely colored substances that can be
  used to produce a significant degree of
  coloration when dispersed in other materials by a
  process which destroys the crystal structure of
  the dye.
• By contrast pigments are aggregated and insoluble.

4
Dyes

• Absorb strongly in the visible region ( 400 800
  nanometers).
• Only organic molecules of considerable complexity
  which contain extensive conjugation systems
  linked to electron withdrawing and attracting
  groups give sufficient absorption in the visible
  region to be useful as dyes.

5
Azo Dyes

• Most important class
• Account for over 50 of all commercial dyes

6
(No Transcript)
7
Made from diazonium
8
Anthraquinone Dyes
9
Indigo

• Blue used for jeans

10
Phthalocyanine

• Analogues of the natural pigments chlorophyll and
  heme
• Unlike the natural pigments, very stable

CI Direct Blue
11
Pigments

• Common pigments are inorganic
• TiO2, ZnO, ZnS for whites
• Iron oxides, chrome oxides also common inorganic
  pigments
• Also some organic pigments chemistry similar to
  organic dyes, but insoluble

12
About 7 million pounds per year of Pigment Blue
Note insoluble since no sodium sulfonate groups
as in CI Direct Blue dye