Strong, moderate, and weak nucleophiles can be categorized as follows: A strong nucleophile contains more un-saturation, such as a double bond or triple bond, or it may be a cyclic structure. Strong nucleophiles may contain atoms with higher electronegativity, or atoms having loosely bound electron pairs. Each of these characteristics make the species more electron rich, which makes it more effective in attacking an electrophilic carbon atom. Moderate nucleophiles are those that increase the availability of an electron pair, usually through an electron-donating effect, but are not as good as strong nucleophiles at attacking an eletrophilic atom. In weak nucleophiles delocalization of an electron pair makes the electron pair less accessible. This delocalization can take place because of the presence of a carbonyl group adjacent to a nucleophilic atom, such as N or O. Neutral molecules are also poor nucleophiles and are less able to attack electrophilic atoms. Sort the following nucleophiles as excellent, good, or poor. A. CH3O-
B. CH3COO-
C. CN-
D. CH3OH
E. HS-
F. HCOOH
G. Br-
H. I-