Organic Chemistry 2 · Amine basicity and electronic structure
Tetramethylguanidine and HCl give tetramethylguanidinium
Conditions: HCl, CH2Cl2
Draw this problem yourself
Drag from the electrons that move to where they go, or tap one and then the other. Every arrow is checked; Hint helps when you're stuck. No account needed.
The mechanism, step by step
Next plays each step's curved arrows and explains them. The written steps are below.
Read all 2 written steps
Protonate the imine nitrogen
The sp2 C=NH nitrogen of tetramethylguanidine is the basic site; the two NMe2 lone pairs are already conjugated with the C=N bond. Protonating the imine nitrogen gives a cation whose charge both NMe2 groups can share.
The curved arrows
- The imine nitrogen lone pair, in an sp2 orbital in the plane of the molecule, forms the new N–H bond to the proton.
- The H–Cl bond pair stays on chlorine, which leaves as chloride; the strong acid makes this transfer essentially complete.
Tetramethylguanidinium chloride
In the guanidinium ion the positive charge is delocalised over all three nitrogens through equivalent C=N⁺ resonance forms. That stabilisation makes tetramethylguanidine (pKaH about 13.6) one of the strongest neutral organic bases.
What you'll practice
Draw the imine nitrogen of tetramethylguanidine taking the proton from HCl.
You just pushed every arrow of this one.
Every one of the 5349 Orgo 1 and Orgo 2 problems works like this: feedback on each arrow, hints when you're stuck, a no-hint quiz mode. Free with an account, no card.
Stuck on your own homework?
Snap it — first scan free, no sign-up
Scanning every week? Scan Standard: for about problems