6. AEMoody: Truman State U
Natural Dyes
Tyrian Purple
From Shellfish
N
N
O
O
H
H
Br
Br
Kermesic Acid
From Insects
HOOC
HO
CH3 O
O OH
OH
OH
7. AEMoody: Truman State U
Molecular Structure
Determines Color of Matter
Note extended conjugated pi systems in
these synthetic dyes:
OH
N
N
SO3
- Na+
Orange II
Martius Yellow
O- NH4
+
NO2
O2N
8. AEMoody: Truman State U
Fiber Structure Determines
Interactions with Dyes
N
H
CH
R
C
O
NH CH
R'
C
O
NH CH
R"
C
O
n
Wool has many reactive sites in its structure:
9. AEMoody: Truman State U
Cheaper Fabric Structures
• In Cotton, R = H
• In Acetate Rayon, R= C(O)CH3
O
O
O
HO
OR
CH2OH
O
O
CH2OH
OH
RO
n
10. AEMoody: Truman State U
Vat Dyes depend on
Mechanical Retention and
Redox Chemistry
N
N
O
O
H
H
Na2S2O4 + NaOH
O2 N
N
H
H
O- Na+
O- Na+
Indigo Indigo white
blue form, H 2O insoluble Leuco form, H 2O soluble
11. AEMoody: Truman State U
Fiber Reactive Dyes
In General: W-D-Q-RG-X
Where:
W = water solubilizing groups
D = Chromophore of Dye
Q = Bridging Group
RG = Reactive Group
X = Leaving Group
12. AEMoody: Truman State U
Procion Synthetic Dye Example
• Fiber Reactive Dye
• Covalently Bonds to Fabric
N
N
N
Cl
Cl
SO3
-
Na
+
NH
SO3
-
Na
+
O
O
NH
Procion Blue
13. AEMoody: Truman State U
“Stylized” Procion Dye
Reaction with Cotton
OH OH OH OH OH
Base
O O O O O
Dye-Cl
O O O O O
Dye Dye Dye Dye Dye
Pretend this is cotton:
Deprotonated "cotton":
Dye BONDED to "cotton":
14. AEMoody: Truman State U
Closer Look at Dye-Fabric
Bond Formation
N
N
N
WDQ Cl
Cl
O Cel
N
N
N
WDQ
Cl
Cl
OCel
N
N
N
WDQ OCel
Cl
+ Cl
15. AEMoody: Truman State U
Hydrolysis of C-Cl of Dye
N
N
N
WDQ Cl
Cl
O H
N
N
N
WDQ Cl
Cl
OH
N
N
N
WDQ OH
Cl
+ Cl
16. AEMoody: Truman State U
Acid-Base Chemistry
Inactivates Dyes
N
N
N
N Cl
Cl
O H
WD
H
N
N
N
N Cl
Cl
WD
H OH
NH
N
N
N Cl
Cl
WD
+ HO
unreactive
17. AEMoody: Truman State U
Today’s Experiment
• Your T-shirt starts out
very clean and dry!
• It goes into our bucket of base solution and
now it is very wet and basic.
• We’ll wring it out
when we give it to you!
18. AEMoody: Truman State U
Your Task for Today
• Twist and fold the damp, basic
shirt in particular patterns;
secure it with rubber bands.
• Apply the dyes using squirt
bottles….
• Place wet, dyed shirt in zip-lock
bag and let reactions proceed.
19. AEMoody: Truman State U
Patience with the Experiment!
• Wait 24 hours!
• Wash in hot water with dish
soap; dry in hot dryer.
• Enjoy cool shirt! ;-)
20. AEMoody: Truman State U
Tie Dye and Chemistry are
FUN!
• Fun and creative outlet
• Excellent outreach activity
• Excellent fund-raising activity
• Chemistry at many levels
;-)
