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In organic chemistry, enols are a type of functional group or intermediate in organic chemistry containing a group with the formula C=C(OH) (R = many substituents). The term enol is an abbreviation of alkenol , a portmanteau deriving from "-ene"/"alkene" and the "-ol".
The equilibrium constant tends to be high in nonpolar solvents; when K keto→enol is equal or greater than 1, the enol form is favoured. The keto form becomes more favourable in polar, hydrogen-bonding solvents, such as water. [7] The enol form is a vinylogous analogue of a carboxylic acid. [citation needed]
In the protonation of an enolate ion, the kinetic product is the enol and the thermodynamic product is a ketone or aldehyde. Carbonyl compounds and their enols interchange rapidly by proton transfers catalyzed by acids or bases, even in trace amounts, in this case mediated by the enolate or the proton source.
The general structure of a silyl enol ether. In organosilicon chemistry, silyl enol ethers are a class of organic compounds that share the common functional group R 3 Si−O−CR=CR 2, composed of an enolate (R 3 C−O−R) bonded to a silane (SiR 4) through its oxygen end and an ethene group (R 2 C=CR 2) as its carbon end.
A weaker base such as an alkoxide, which reversibly deprotonates the substrate, affords the more thermodynamically stable benzylic enolate. Enolates can be trapped by acylation and silylation, which occur at oxygen. Silyl enol ethers are common reagents in organic synthesis as illustrated by the Mukaiyama aldol reaction: [13]
In organic chemistry an enol ether is an alkene with an alkoxy substituent. [1] The general structure is R 2 C=CR-OR where R = H, alkyl or aryl. A common subfamily of enol ethers are vinyl ethers, with the formula ROCH=CH 2. Important enol ethers include the reagent 3,4-dihydropyran and the monomers methyl vinyl ether and ethyl vinyl ether.
Oxidative functionalization of silyl enol ethers in low concentration (to avoid homocoupling) without an external nucleophile leads to dehydrogenation. This can be a useful way to generate α,β-unsaturated carbonyl compounds in the absence of functional handles.
By contrast, stable solutions of pure enolate ions are easily prepared from most carbonyl compounds by reaction with a strong base. Second, enolate ions are more reactive than enols and undergo many reactions that enols don't. Whereas enols are neutral, enolate ions are negatively charged, making them much better nucleophiles.