Polyvinyl alcohol is a high molecular weight polymer whose repeating unit is CH2-CHOH. From this the expected monomer from which polyvinyl alcohol would be produced is vinyl alcohol, CH2=CHOH, however, vinyl alcohol does not exist in the free state, for it is very unstable in nature. Apparently, all reactions which would yield vinyl alcohol undergo a rearrangement to the more stable acetaldehyde or keto form. double bond in vinyl alcohol. This is caused by the desire to relieve the strain of the Rearrangements of this enol-keto type take place particularly easily because of the polarity of the 0-H bond and the very high electron density that attempts to become more stable by shifting a hydrogen. To relieve this strain, a hydrogen ion separates readily from oxygen, but when a hydrogen ion (most likely a different one) returns it may attach itself either to oxygen or to carbon. If it returns to oxygen, it may readily come off again; but if it attaches itself to carbon it tends to stay there.