4-Dimethylaminopyridine

For the cyanide antidote, see 4-Dimethylaminophenol.

4-Dimethylaminopyridine

100px
Names
IUPAC name 4-dimethylaminopyridine
Systematic IUPAC name 4-(dimethylamino)azine N,N-dimethyl-4-aminoazine 4-(dimethylamino)azabenzene N,N-dimethyl-4-aminoazabenzene
Other names 4-(dimethylamino)pyridine N,N-dimethyl-4-aminopyridine DMAP
Identifiers
CAS Number	1122-58-3 Y
ChemSpider	13646 Y
Jmol 3D model	Interactive image
PubChem	14284
InChI InChI=1S/C7H10N2/c1-9(2)7-3-5-8-6-4-7/h3-6H,1-2H3 Y Key: VHYFNPMBLIVWCW-UHFFFAOYSA-N Y InChI=1/C7H10N2/c1-9(2)7-3-5-8-6-4-7/h3-6H,1-2H3 Key: VHYFNPMBLIVWCW-UHFFFAOYAL
SMILES n1ccc(N(C)C)cc1
Properties
Chemical formula	C7H10N2
Molar mass	122.17 g/mol
Appearance	white solid
Melting point	110 to 113 °C (230 to 235 °F; 383 to 386 K)
Boiling point	162 °C (324 °F; 435 K) at 50 mmHg
Acidity (pKa)	9.6 in water, 17.95 (pKa of conjugate acid in acetonitrile)
Vapor pressure	{{{value}}}
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Y verify (what is YN ?)
Infobox references

4-Dimethylaminopyridine (DMAP) is a derivative of pyridine with the chemical formula (CH₃)₂NC₅H₄N. This colourless solid is of interest because it is more basic than pyridine, owing to the resonance stabilisation from the NMe₂ substituent.

Because of its basicity, DMAP is a useful nucleophilic catalyst for a variety of reactions such as esterifications with anhydrides, the Baylis-Hillman reaction, hydrosilylations, tritylation, the Steglich rearrangement, Staudinger synthesis of β-lactams and many more. Chiral DMAP analogues are used in kinetic resolution experiments of mainly secondary alcohols and Evans auxiliary type amides.

Preparation

DMAP can be prepared in a two-step procedure from pyridine, which is first oxidized to 4-pyridylpyridinium cation. This cation then reacts with dimethylamine:

450px

Esterification catalyst

Main article: Steglich esterification

In the case of esterification with acetic anhydrides the currently accepted mechanism involves three steps. First, DMAP and acetic anhydride react in a pre-equilibrium reaction to form an ion pair of acetate and the acetylpyridinium ion. In the second step the alcohol adds to the acetylpyridinium, and elimination of pyridine forms an ester. Here the acetate acts as a base to remove the proton from the alcohol as it nucleophilically adds to the activated acylpyridinium. The bond from the acetyl group to the catalyst gets cleaved to generate the catalyst and the ester. The described bond formation and breaking process runs synchronous concerted without the appearance of a tetrahedral intermediate. The acetic acid formed will then protonate the DMAP. In the last step of the catalytic cycle the auxiliary base (usually triethylamine or pyridine) deprotonates the protonated DMAP, reforming the catalyst. The reaction runs through the described nucleophilic reaction pathway irrespective of the anhydride used, but the mechanism changes with the pKa value of the alcohol used. For example, the reaction runs through a base-catalyzed reaction pathway in the case of a phenol. In this case, DMAP acts as a base and deprotonates the phenol, and the resulting phenolate ion adds to the anhydride.

Safety

DMAP has a relatively high toxicity and is particularly dangerous because of its ability to be absorbed through the skin. It is also corrosive.

Further reading

• ;