Dipole-Bound Anions of 28 molecules containing either a carbonyl, nitrile, sulfoxide, or sulfite group were studied using Rydberg Electron Transfer (RET) reactions with rubidium atoms excited to ns 2S and nd 2D excited states. The electron affinity of each molecule was obtained from the Rydberg state, n*max, that gave the largest negative ion yield using the empirical relationship EA=23/n*max2.8 eV as well as from fitting the charge exchange profile to a theoretical curve crossing model. Electron affinities for the low dipole moment molecules (carbonyls) were also calculated from measurements of the electric field required to detach the electron from the anion. The dependences of the electron affinity upon dipole moment, polarizability, conformation, and geometry of the molecules are investigated. The effect of collision velocity on the creation of these anions is studied through the use of different carrier gases (H2, He, Ne, Ar, Kr, Xe) in the nozzle jet expansion. Competition between RET and collisional detachment is observed and discussed qualitatively.