8M, Azo Dyes & Indigo Synthesis L6-1 CHEM 8M, Lecture 6 Exp 4, Week 1 – Synthesis & Application of Azo Dyes - Nature of color - Dye to Fabric Interactions - Diazonium Coupling Outcomes: Observe effects of dye structure, fibers, and metals (mordants) on appearance Synthesis of Azo Dyes Part A Diazotization Make & cool two solutions in two test tubes before mixing… then…Gravity filtration Diazotization Mechanism – what’s happening??!! Fill in the arrows at each step. NH 2 NaNO 2 HCl N N Cl - Diazotization Benzenediazonium chloride a "diazonium salt" OH Coupling N N OH NH 2 NaNO 2 HCl, H 2 O Diazonium chloride salt of 4-nitroaniline O 2 N O 2 N N 2 + Cl - N N Cl = 4-nitroaniline (Substrate) O 2 N ice bath slowly add acid to substrate drop-wise in ice bath gravity filter over ice NO O H Cl N OH O H Cl NO nitrosonium ion Ar-NH 2 Ar N H H N O Ar N H H N O H Cl Ar N N OH H Cl N N + H 2 O H 2 O H
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8M, Azo Dyes & Indigo Synthesis
L6-1
CHEM 8M, Lecture 6 Exp 4, Week 1 – Synthesis & Application of Azo Dyes - Nature of color - Dye to Fabric Interactions - Diazonium Coupling Outcomes: Observe effects of dye structure, fibers, and metals (mordants) on appearance Synthesis of Azo Dyes
Part A Diazotization
Make & cool two solutions in two test tubes before mixing… then…Gravity filtration
Diazotization Mechanism – what’s happening??!! Fill in the arrows at each step.
NH2NaNO2
HCl
NN
Cl-Diazotization
Benzenediazoniumchloride
a "diazonium salt"
OH
Coupling N N
OH
NH2 NaNO2
HCl, H2O
Diazonium chloride salt of 4-nitroaniline
O2N O2N
N2+Cl-NNCl
=
4-nitroaniline (Substrate)
O2N
icebath
slowly add acid to substrate
drop-wisein ice bath
gravity filter
over ice
N OOH Cl
N OHOH Cl
N Onitrosonium
ion
Ar-NH2Ar N
H
H
NO
Ar NH
H
NO
H ClAr N N
OH
H Cl NN
+ H2O
H2O
H
8M, Azo Dyes & Indigo Synthesis
L6-2
Part B Diazo Coupling via Ingrain Dyeing - Diazo coupling is a type of Electrophilic Aromatic Substitution (EArS) reaction (McM Ch 16) - Propose arrow-pushing mechanisms for the synthesis of American flag red (1 intermediate)
Apply EArS mechanism to easter purple… Ingrain Dyeing = The reaction takes place on the fabric swatch!
Mordant Dyeing - Fabric strip is pre-treated with coordinating metal: Cu2+, Al3+, or Fe2+ - Pre-made swatches with copper (II) sulfate, aluminum potassium sulfate, or iron (II) sulfate - Use same ingrain dye procedure above with ‘mordant fabrics’ - How does this effect dye – fiber interactions?
Direct Dyeing
Logistics: Exp 4, page 5 includes…
Team Cat Pair closer to the chalkboard
Team Dog Pair farther from the chalkboard
Day 1 *Part A *American Flag Red *B.1 - ingrain dyeing * Part C – mordant dyeing
*Part A *Easter Purple *B.2 - ingrain dyeing * Part C – mordant dyeing
Print Table 3 (page 12) and bring with you to lab both days.
Day 2 *Part D - indigo
*Part E (Malachite green) *Part D - indigo *Part E (Eosin Y)
O
O
OOH
Al3+
NH NHFiber
OH2H2O
N(CH3)2+X-
N(CH3)2
Malachite Green
OHOBr
HO
Br
Br
Br
Eosin Y
O
O
8M, Azo Dyes & Indigo Synthesis
L6-4
Exp 4, Day 2: INDIGO SYNTHESIS & VAT DYEING Part D.1. Synthesis
EXPERIMENTAL METHODS – Part D.1 (Indigo synthesis) only Draft due as part of next week’s pre-lab – you can write it before you do it! Use xx or _____ in place of results. General Methods All reagents were commercially available. Experimental Methods - Reaction scheme - Product name - Chemical names (# mg, # mmol) - Order of addition - Temperature, time - Filtration, washes, drying time - No characterization Last sentence: “Indigo was isolated as a blue solid (xx mg, xx mmol).” Next week in lab: Synthesis & Application of Azo Dyes Next week in lecture: Indigo Dye & 1H NMR Splitting in Esters