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Reaction MechanismsIntroductionCorrect drawings of reaction mechanisms are central to organic chemistry. This does not only mean that the mechanism themselves are correct. More importantly, this means that the drawings follow certain conventions. How to draw organic reaction mechanismsThe most important concept in drawing organic rection mechanisms is that of electron flow indicated by curly arrows. By convention the electron flow goes from negative to positive. In the first example below the oxygen lone pair (negative) attacks the proton (positive). In the second example the nucleophile attacks the central carbon and expells the leaving group.
It is of vital importance that your drawings of organic reaction mechanisms contain curly arrows to reflect the electron flow. As you get used to this you will notice that it also helps to remember multi-step reaction mechanisms. Indeed, it should not be necessary to memorize reaction mechanisms, because they reflect the electron flow. If your mechanism reflects the flow of electrons without violating any fundamental rules your mechanism will be correct - even if it is not exactly the same as in the text books. Examples1. Acid-Catalysed Hydrolysis of AcetalsA very important reaction and a good example to practise drawing reaction mechanisms is the acid catalysed hydrolysis of ketals (acetals). Double click on the drawing below to see the animated reaction mechanism (note: the animation loads into a new browser window and plays twice. If you want to see it again, close the window and double click the drawing below again.)
Click here to see the complete reaction diagram. 2. Acid-Catalysed Hydrolysis of EstersEster hydrolysis can be achieved under acidic and basic conditions. Under acidic conditions the hydrolysis proceeds commonly via the following mechanism:
Double click on the drawing above to see the animated reaction mechanism (note: the animation loads into a new browser window and plays twice. If you want to see it again, close the window and double click the drawing below again.) Click here to see the complete reaction diagram. Double click on the drawing above to see the animated reaction mechanism (note: the animation loads into a new browser window and plays twice. If you want to see it again, close the window and double click the drawing below again.) Click here to see the complete reaction diagram. 4. How to draw Six-Membered RingsIt is essential to draw six-membered rings correctly. Follow the instructions below. Double click on the drawing above to see the animated reaction mechanism (note: the animation loads into a new browser window and plays twice. If you want to see it again, close the window and double click the drawing below again.)
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