Organic Chemistry chp. 15 terms

addition in which two atoms or groups add to adjacent atoms

addition in which two atoms or groups add to atoms that have a 1,4-relationship

common name for the 2-propenyl group, -CH2-CH2-=CH2-

carbon atom next to a C=C bond, eg. allylic cation, allylic radical, allylic anion

isomerization of a double bond occuring through delocalization of an allylic intermediate

reaction in which all bond making and braking occurs in the same step, eg. E2, SN2, Diels-Alder

double bonds alternating with single bonds, interaction by p orbitals overlaping in the pi bonds

double bonds separated by two or more single bonds, react like a simple alkene

successive double bonds with no single bonds in between

compound containing cumulated C=C bonds

pericyclic reaction theory in which the MOs of the reactants flow directly into the MOs of the products with out significant changes in symmetry, bonding interactions stabilize the transition state

overlap of orbitals that contributes to bonding, generally overlap of lobes with similar phases, eg. + with + or - with -

reaction of two alkenes or polyenes to form a cyclic product, often through concerted interactions of pi e- in two unsaturated molecules

molecular orbital resulting from the combination of three or more atomic orbitals, when filled orbitals spread e- density over all the atoms

overlap of orbitals contributing to antibonding, generally overlap of lobes with opposite phases, eg + with -

synthesis of six membered ring by [4 + 2] cycloaddition, four pi e-’s in one molecule interact with 2 pi e-’s in the other molecule to form a new ring

component with 2 pi e-’s interacts with diene in Diels-Alder reaction

stereochemical preference for electron-poor substituents in the dienophole endo positions of a bicyclic Diels-Alder product

overlap of p orbital e- withdrawing groups of the dieneophile with one of the central atoms of the diene, helps stabilize transition state, favors endo products in cyclic dienes

enthalpy of reaction accompanying addition of hydrogen to a mole of an unsaturated compound

highest occupied molecular orbital, in a photochemically excited state this orbital is represented as HOMO*

product distribution governed by rates at which products form

product that is formed fastest, the major product under kinetic control

lowest unoccupied molecular orbital

measure of how strongly a compound absorbs light at a particular wavelength, Beers law A = log (Ir /Is) = Ecl, A is the absorbance, Ir and Is are the amount of light passing through the reference and the sample, c is the sample concentration in moles per liter, l is the length of light passing through the cell

orbitals that contain more than one atom in the molecule, can be bonding, antibonding or nonbonding

MO’s lower in energy than individual MO’s from which they were made, e-’s in these orbitals hold the atoms together

MO’s higher in energy than the individual MO’s from which they were made, e-’s in these orbitals push atoms apart

MO’s with the same energy as the individual MO’s from which they were made, e- in these orbitals have no effect on the atoms

a region of molecular orbital with zero e- density

reaction involving concerted reorganization of e-’s in a closed loop of interacting orbitals, one class are cycloadditions

a second beam passes through the reference cell containing only the solvent, the sample beam is compared to this beam to compensate for absorption by the cell or the solvent

extra stabilization by delocalization compared to a localized structure, in dienes and polyenes resonance energy is extra stability of the conjugated system compared to a compound with and equivelent number of independent bonds

cis-like conformation of a single bond in a conjugated diene or polyene

trans-like conformation of a single bond in a conjugated diene or polyene

MO’s of the reactants may flow into the MO’s of the products in one concerted step according to rules of conservation of orbital symmetry, in symmetry-allowed cycloaddition there is constructive overlap between the HUMO of one molecule with the LUMO of the other

MO’s of the reactants are of incorrect symmetries to flow into those of the products in one concerted step

product distribution is governed by stability of the products, operates when the reaction is allowed to come to equilibrium

most stable product, major product under thermodynamic control

measurement of the absorption of ultraviolet and visible light as a function of wavelength, UV wavelength 100-400nm, visible wavelength 400-750nm

rules that correlate values of ?max in the UV-visable spectrum with structures of conjugated systems

symmetry rules that predict whether a pericyclic reaction is symmetry-allowed or symmetry-forbidden