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!

OH2-Naphthol

NN

OHNO2

American Flag Red

NN

Cl

NO2

ANS

HN

+H4N-O3S

NN NO2

Easter Purple

NN

Cl

NO2HN

+H4N-O3S

Part B.1 - Cat Team

Part B.2 - Dog Team

250 mLbeaker NaOH +

2-napthol or ANS

fabric swatch fabric swatch treatedwith pre-cursor

100 mLbeaker diazo salt

+ water

warm plate

watch glass ingrain dyedfabric swatch

8M, Azo Dyes & Indigo Synthesis

L6-3

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

H

O

NO2

+O NaOH

HN

NHO

O

Blue Indigowater-insoluble

2

ortho-nitrobenzaldehyde(ONB)