Molecules: You'd better learn to live with them.
The dimethoxytrityl, or DMT, ligand, is one of my favorite protecting groups in organic chemistry. Oftentimes, you need to "mask" part of a molecule to keep it from reacting during a step in a synthesis. DMT does this without breaking a sweat and gives you pretty colors to look at to boot.
Those phenyl rings form a pinwheel type arrangement (in 3-D, that is, they're twisted out of the plane of your screen).
When bound to a molecule, DMT doesn't have much of a color. When it's removed with acid, though, you actually get a (rare, usually unstable and only transient) solution of dimethoxytrityl cation - carbon with only three bonds! (Otherwise, it always has four). This unusual species has a brilliant orange-yellow Kool-Aid color, and is perfectly stable in solution. I've had some sitting on my bench for days now. When you isolate your (now deprotected) compound, you probably end up with something colorless again. If you add water to your DMT cation, the color fades and you just end up with dimethoxytrityl alcohol.
DMT is a generally useful protecting group, but perhaps the most famous (and certainly the most ubiquitous by far) use of DMT is in the automated synthesis of short strands of DNA.
Comments
this entire thing is completly innaccurate.
Posted by: Kelly Nordberg | September 4, 2007 2:45 AM