CO2 is a lewis acid as it can accept electrons. But as the octets of all atoms of CO2 are complete why does it accept electrons? Shouldn't it donate electrons and be a lewis base?
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4$\begingroup$ Most of the stable compounds have complete octets on all atoms. This has nothing to do with their willingness to donate or accept electrons. $\endgroup$– Ivan NeretinMay 1, 2016 at 15:31
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$\begingroup$ @IvanNeretin Then how do we determine it? $\endgroup$– user456May 1, 2016 at 15:33
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1 Answer
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Consider that the carbon in carbon dioxide is bonded to two electronegative oxygen atoms. This will cause shift the electrons towards the oxygens and away from the carbon, making it electron deficient:
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This makes the central carbon electrophilic, and explains the reactivity of the carbonyl moiety towards nucleophiles. Similarly, $\ce{CO2}$ undergoes addition reactions with Grignard reagents to form carboxylate anions.
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