Consequences of Acid Strength and Solvation in Catalysis Mediated by Ion-pair Transition States

2012 Spring Symposium

Enrique Igle­sia
Depart­ment of Chem­i­cal Engi­neer­ing
Uni­ver­si­ty of Cal­i­for­nia at Berke­ley and Chem­i­cal Sci­ences Divi­sion
E.O. Lawrence Berke­ley Nation­al Lab­o­ra­to­ry

Abstract — The rate and selec­tiv­i­ty of reac­tions cat­alyzed by acids depend on the sta­bil­i­ty of ion-pairs at tran­si­tion states that medi­ate kinet­i­cal­ly-rel­e­vant steps. Rates and selec­tiv­i­ties for alka­nol dehy­dra­tion and homolo­ga­tion, alkene and cycloalkene iso­mer­iza­tion, and alkox­ide scis­sion and hydro­gen trans­fer on poly­ox­omet­a­late and zeolitic acids show that sen­si­tiv­i­ty to acid strength reflects dif­fer­ences in the amount and dif­fuse­ness of the charge in the rel­e­vant pre­cur­sors and the tran­si­tion states. The effects of sol­va­tion by con­fine­ment on rates and selec­tiv­i­ties depend, in turn, on their respec­tive dif­fer­ences in size. The known struc­tures of these acids allow rig­or­ous com­par­isons between exper­i­ment and the­o­ry, which con­firm the mech­a­nis­tic inter­pre­ta­tions of rate data and the rel­e­vance of depro­to­na­tion ener­gies as the­o­ret­i­cal prox­ies of acid strength. These stud­ies and insights sug­gest a rig­or­ous reac­tiv­i­ty-based rank­ing of acid strength that can be used to assess the strength of sol­id acids with uncer­tain or non-uni­form struc­tures.

Speaker’s Biog­ra­phy — Enrique Igle­sia is the Theodore Ver­meulen Chair in Chem­i­cal Engi­neer­ing at the Uni­ver­si­ty of Cal­i­for­nia at Berke­ley and a Fac­ul­ty Senior Sci­en­tist in the Lawrence Berke­ley Nation­al Lab­o­ra­to­ry. He received his B.S. from Prince­ton Uni­ver­si­ty and his Ph.D. degree from Stan­ford Uni­ver­si­ty with Pro­fes­sor Michel Boudart and joined the Berke­ley fac­ul­ty in 1993 after 12 years in research and lead­er­ship posi­tions at the Cor­po­rate Research Labs of Exxon. He has served as Edi­tor-in-Chief of Jour­nal of Catal­y­sis and is the Pres­i­dent of the North Amer­i­can Catal­y­sis Soci­ety and the Direc­tor of the Berke­ley Catal­y­sis Cen­ter. He has co-authored more than 300 arti­cles in the lead­ing jour­nals in chem­istry and chem­i­cal engi­neer­ing and is a co-inven­tor in 38 U.S. patents. He is a mem­ber of the Nation­al Acad­e­my of Engi­neer­ing and a Fel­low of the Amer­i­can Chem­i­cal Soci­ety. His research has been rec­og­nized with the Somor­jai and Olah Awards of the Amer­i­can Chem­i­cal Soci­ety, the Award for Excel­lence in Nat­ur­al Gas Con­ver­sion, the Alpha Chi Sig­ma and Wil­helm awards of the Amer­i­can Insti­tute of Chem­i­cal Engi­neers, the Emmett and Bur­well Awards of the Catal­y­sis Soci­ety, the Tan­abe Prize in Acid-Base Catal­y­sis, the Cana­di­an Chem­i­cal Soci­ety Cross Cana­da Lec­ture­ship, and the Fran­cois Gault Award of the Euro­pean Fed­er­a­tion of Catal­y­sis Soci­eties. His research inter­ests include the syn­the­sis and struc­tur­al and mech­a­nis­tic char­ac­ter­i­za­tion of nov­el inor­gan­ic solids use­ful as cat­a­lysts in chem­i­cal reac­tions of crit­i­cal impor­tance in ener­gy con­ver­sion, sus­tain­able syn­the­sis of ener­gy car­ri­ers and petro­chem­i­cals, and pol­lu­tion pre­ven­tion and envi­ron­men­tal con­trol.