What does the N designation mean in organic chemistry? For example: N-hydroxymethylurea?
It just emphasizes how the substituent is attached to a nitrogen. That's all! :) Since urea is an amide, it follows amine/amide naming conventions that specify when a substituent is bound onto a nitrogen and not bound onto something else.
You probably meant to say N-(hydroxymethyl)urea.
Another name for it is methylolurea; ol nicely emphasizes that it's an alcohol group attached to urea in some way, and methyl emphasizes that it's not a
Also, be careful that you don't confuse hydroxymethyl with methoxy (I sometimes do). Hydroxymethyl implies an alcohol substituent, but methoxy is an alkoxide (deprotonated alcohol) substituent.
N-(hydroxymethyl)urea says that a
As an aside, if you wrote:
Then it shows that the first nitrogen emphasized (N) is not the same as the second nitrogen emphasized (N'), and each singular methyl is on a different nitrogen.