Exam Uno Questions

After taking the first Organic Chemistry exam, I wondered why there was not a question that required us to label and count the number of ¹H NMR signals for different compounds.  After working hard and completing the Sapling homework I fully understood and knew I was able to answer these questions.  On Sapling, there were a few questions that covered this portion of Organic Chemistry.  When the exam was handed out I was confused on why there wasnt any of these choices of questions on there.  The correct way to answer these types of questions is to make sure to understand that the number of NMR signals equals the number of different types of protons in a compound.  The main principle of finding the number of signals is that protons in different environments give different NMR signals.  The same NMR signals are given by protons being equivalent to each other.  For example, a compound such as CH₃OCH₃ has only one ¹H NMR signal.  The reasoning for this is that each methyl group CH₃ is bonded to the same group which makes both methyl groups have the same signal.  However, for a compound such as CH₃CH₂Cl there are two different signals because the hydrogens are two carbons away from the chlorine for one signal and for the other signal the hydrogens are located one carbon away.  After working on the sapling problems and reading over this section in the book I was confident that I would be able to complete a question on the number of ¹H NMR signals.  However, since there was not a question on the exam containing this subject I was a little confused but this is still a great part of Organic Chemistry that needs to be understood.