The preparation of azo dyes is a standard reaction in the sophomore organic chemistry lab. Its adaptation to a parallel synthesis format is straightforward and the assay is trivial.Since the dyes vary widely in color, the diversity of this parallel synthesis becomes obvious. Organic topics of diazotization, electrophilic aromatic substitution and various analytical techniques enter into the discussion.

1. Acid and direct dyes-Organic Chem
prelab
By Dr. Robert D. Craig, Ph.D.

2. .

3. •
. group or EWG draws
An electron withdrawing
electrons away from a reaction center. When
this center is an electron rich carbanion or an
alkoxide anion with the presence of the
substituent that has a stabilizing effect.
• Examples of electron withdrawing groups are
• halogens (F, Cl);
• nitriles CN;
• carbonyls CO;
• nitro groups NO2.

4. .
• A carbanion is a nucleophile. The stability and
reactivity of a carbanion is determined by several
factors. These include
• 1. The inductive effect. Electronegative atoms
adjacent to the charge will stabilize the charge;
• 2. Hybridization of the charge-bearing atom. The
greater the s-character of the charge-bearing
atom, the more stable the anion;
• 3. The extent of conjugation of the anion.
Resonance effects can stabilize the anion.

5. .

6. A carbocation (No octet rule).
• A carbocation is an ion with a positively-
charged carbon atom. The charged carbon
atom in a carbocation is a "sextet", i.e. it has
only six electrons in its outer valence shell
instead of the eight valence electrons that
ensures maximum stability (octet rule).

7. carbocations.
• An electron releasing group or ERG
(otherwise called electron donating groups or
EDG) releases electrons into a reaction center
and as such stabilizes electron deficient
carbocations.
• Examples of electron releasing groups are
• alkyl groups;
• alcohol groups;
• amino groups.

8. .

9. .
• a carbocation is often the target of
nucleophilic attack by nucleophiles like
hydroxyl (OH−) ions or halogen ions.