Fall 2019HFH1104

Armen ZakarianOffice: Chemistry Bldn 2217

Chem 109 CBioorganic Compounds

http://labs.chem.ucsb.edu/~zakariangroup/courses.html

CLAS Instructor: Dhillon Bhavanbdhillon@ucsb.edu

METAL-ION CATALYSIS

suggested additional exercise: fill in the blanks throughout these slides

METAL-ION CATALYSIS

catalysis through coordination of the metal ions to substrate

METAL-ION CATALYSIS

examples: decarboxylation

OO

OO

O

OO

O

OO

O

OO

O

H++ C

O

O

METAL-ION CATALYSIS

examples: hydrolysis

METAL-ION CATALYSIS

examples: hydrolysis

PROBLEM 8 The hydrolysis of glycinamide is catalyzed by Co2+, Propose a mechanism for this reaction

NH2

OH2N O-

OH2N+ H2O

Co2+

+ NH4+

INTRAMOLECULAR CATALYSIS

intramolecular and intermolecular reactions why are intramolecular reactions faster?

OHHO

O

CH3+

O

+ H2O

CH3

O

OH

O

OH O

O

~1015 times faster+ H2O

intermolecular reaction:

intramolecular reaction:

“intramolecular catalysis”, “neighboring group participation”, “anchimeric assistance”are interchangeable terms

INTRAMOLECULAR REACTIONS

reaction rate

fraction with proper orientation

fraction with sufficient energy~

number of collisions per unit time ××

INTRAMOLECULAR REACTIONS

reaction rate

fraction with proper orientation

fraction with sufficient energy~

number of collisions per unit time ×

relative rate Ms-1

s-1 M-1= first order k second order k= =

effective molarity

kintramol kintermol

=

×

10

11

12

13

14

INTRAMOLECULAR CATALYSIS

“catalyst” is a part of the reacting moleculeintramolecular general base catalysis:

INTRAMOLECULAR CATALYSIS

“catalyst” is a part of the reacting moleculeintramolecular metal catalysis:

INTRAMOLECULAR CATALYSIS

!  why is this 70,000 times faster?!  what type of catalysis is this?

“catalyst” is a part of the reacting moleculeintramolecular nucleophilic catalysis:

INTRAMOLECULAR CATALYSIS

Cl

SPh

Cl

SPh

cis vs. trans

•  conformational analysis•  stereochemistry of products•  other examples of neighboring group participation

“intramolecular catalysis”, “neighboring group participation”, “anchimeric assistance”are interchangeable terms

Cl

SPh

OH

SPh

OEt

SPh+

EtOH, H2O+ HCl

in more detail...