UCLAstudent said:And I took what I said out of my chem. textbook, as well.
Since we seem to have conflicting sources, I am going to guess that it depends on what exactly the substituents are. If the electron-donating groups are all methyls, then it's likely that tertiary will be most basic because methyl groups aren't so big. If the groups are phenyls, that may be enough steric hindrance to cause secondary to be more basic.
Just a thought.
babinski bob said:Remember the MCAT is a thinking test. The idea is that alkyl groups are e- releasing. 3 > 2 > 1 > NH3. Don't confuse steric hindrance w/ basicity. Steric hindrance will certainly decrease nucleophilicity but NOT basicity. I can positively 100% confirm this statement.
babinski bob said:The reason why there's different answers and opinions regarding this question is that when looking at basicity, you have to consider solvent effects. Therefore, you'll find different answers depending on the solvent used. In the gaseous phase (where there is no solvent) which is the truest measurement of inherent acidity/basicity, basicities follow 3>2>1>NH3. In some solvents the trend might be 2>3>1>NH3. The MCAT is not interested in testing you on PhD level theory. In all liklihood, you wouldnt get a question asking you to rank trimethyl, dimethyl, methylamine, ammonia. You should however, understand that alkyl groups are e- donating andwill therefore increase the basicity. Therefore, dimethylamine is always more basic than ammonia. And both of these guys are more basic than aniline. These are the types of important concepts to know. You guys seem like you already understand this quite well. Good luck with the mcat. Keep it simple and you'll rock the ochem questions.
blz said:I couldn't agree anymore. KEEP IT SIMPLE! from what I've seen in the MCAT quiz thread, you guys are losing sight of this concept.