Micellar Catalysis

Micellar catalysis, conducted in the absence of Lewis acid tends to inhibit the Diels-Alder reaction, relative to the reaction in water. The reason is that the local reaction medium in the Stern region is less favorable than bulk water. However, by combining Lewis-acid and micellar catalysis, enzyme-like rate accelerations can be obtained (Table 7.5) in case the Lewis acid acts as the counterion for the micelle.14

Figure 7.9 Mechanistic interpretation for catalysis by Lewis acids containing aromatic a-amino acids as ligands.

Figure 7.9 Mechanistic interpretation for catalysis by Lewis acids containing aromatic a-amino acids as ligands.

Amino acid ligand

Dienophile

TABLE 7.5 Solvent Effects and Combined Lewis-Acid/Micellar Catalysis Increasing the Rate Constant of Reaction (1)

Solvent [Cu2+] (mM) Relative k2

TABLE 7.5 Solvent Effects and Combined Lewis-Acid/Micellar Catalysis Increasing the Rate Constant of Reaction (1)

Solvent [Cu2+] (mM) Relative k2

ch3cn

0

1

EtOH

0

2.7

Water

0

287

CF3CH2OH

0

485

ch3cn

10

158.000

EtOH

10

54.900

Water

10

691.000

CF3CH2OH

0.10

1.110.000

Cu (DS)2 micelles

10

1.790.000

Note: DS is n = dodecyl sulfate.

Note: DS is n = dodecyl sulfate.

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