The molecular formula C2H4O2 can correspond to several distinct skeletal…
CHEMISTRY · Multi-part · AP · Chemistry · Compound Structure and Properties · Compound Structure and Properties
Problem
The molecular formula C2H4O2 can correspond to several distinct skeletal connectivities in which the two carbon atoms are directly bonded to each other. A chemist wishes to enumerate every such connectivity and evaluate their relative plausibility.
Address the prompts below in sequence.
(a) Calculate the total number of valence electrons in C2H4O2.
(b) List every unique skeletal connectivity that (i) contains a direct C–C bond, (ii) satisfies the normal valences of all atoms, and (iii) does not place any hydrogen atoms on oxygen unless required for valence satisfaction. Provide a brief textual description of each connectivity (for example, “one carbonyl carbon singly bonded to the second carbon, which bears a hydroxyl group”).
(c) For each connectivity in part (b), draw all valid Lewis diagrams, including any important resonance forms, and label all formal charges.
(d) Rank the connectivities from most to least stable on the basis of formal-charge minimization and the placement of any negative charge on more electronegative atoms. Provide a clear justification for your ranking that refers explicitly to features of the Lewis structures you have drawn.