Π Molecular Orbitals of Ethene
Chem 104A, UC, Berkeley Molecular Orbitals of Ethene Chem 104A, UC, Berkeley 1 Chem 104A, UC, Berkeley Molecular Orbital Analysis of Ethene Dimerisation the reaction is said to be a "symmetry forbidden" – interestingly, this reaction is rare and very slow ! Chem 104A, UC, Berkeley Molecular Orbitals of 1,3-Butadiene 2 Chem 104A, UC, Berkeley Chem 104A, UC, Berkeley Molecular Orbital Analysis of Diels-Alder reaction 3 Chem 104A, UC, Berkeley Acid-Base Chemistry Reading : MT 6 Chem 104A, UC, Berkeley The Acid Base Theory of Brønsted and Lowry In 1923, within several months of each other, Johannes Nicolaus Brønsted (Denmark) and Thomas Martin Lowry (England) published essentially the same theory about how acids and bases behave. •An acid is a "proton donor." •A base is a "proton acceptor." 4 Chem 104A, UC, Berkeley + HCl + H2O <===> H3O + Cl¯ HCl - this is an acid, because it has a proton available to be transfered. H2O - this is a base, since it gets the proton that the acid lost. Now, here comes an interesting idea: + H3O - this is an acid, because it can give a proton. Cl¯ - this is a base, since it has the capacity to receive a proton. + Notice that each pair (HCl and Cl¯ as well as H2O and H3O differ by one proton (symbol = H+). These pairs are called conjugate pairs. Chem 104A, UC, Berkeley HCl + NaOH ---> H2O+ NaCl stronger stronger Weaker weaker conjugate conjugate acid base acid base + - NH4 +OH---> H2O+ NH3 stronger stronger weaker weaker conjugate conjugate acid base acid base 5 Chem 104A, UC, Berkeley H n A H 2O H n1 A H3O [H n1 A ][H3O ] pKa1 log [H n A] pKa 0 strong pKa 0 weak Chem 104A, UC, Berkeley Amphoteric Compound H n A H 2O H n1 A H3O NH 3 H 2O NH 4 OH 6 Chem 104A, UC, Berkeley Oxyacids AOp(OH)q A=Si, N, P, As, S, Se, Te, Cl, Br, I p=# of nonhydrogenated oxygen atom H + A ----O As atom A is rendered more positive, it becomes easier to break the O-H bond Because of enhanced bond polarization.
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