In organic chemistry, keto-enol tautomerism refers to a chemical equilibrium between a keto form (a ketone or an aldehyde) and an enol. The enol and keto forms are said to be tautomers of each other. The interconversion of the two forms involves the movement of a proton and the shifting of bonding electrons; hence, the isomerism qualifies as tautomerism.A compound containing a carbonyl group (C=O) is normally in rapid equilibrium with an enol tautomer, which contains a pair of doubly bonded carbon atoms adjacent to a hydroxyl (−OH) group, C=C-OH. The keto form predominates at equilibrium for most ketones. Nonetheless, the enol form is important for some reactions. Furthermore, the deprotonated intermediate in the interconversion of the two forms, referred to as an enolate anion, is important in carbonyl chemistry, in large part because it is a strong nucleophile.
Keto-enol tautomerism is important in several areas of biochemistry. The high phosphate-transfer potential of phosphoenolpyruvate results from the fact that the phosphorylated compound is "trapped" in the less stable enol form, whereas after dephosphorylation it can assume the keto form. Rare enol tautomers of the bases guanine and thymine can lead to mutation because of their altered base-pairing properties.In certain aromatic compounds such as phenols the enol is important due to the aromatic character of the enol but not the keto form. Melting the naphthalene derivative 1,4-dihydroxynaphthalene 1 at 200 °C results in a 2:1 mixture with the keto form 2. Heating the keto form in benzene at 120°C for three days also affords a mixture (1:1 with first order reaction kinetics) The keto product is kinetically stable and reverts back to the enol in presence of a base. The keto form can be obtained in a pure form by stirring the keto form in triflic acid and toluene (1:9 ratio) followed recrystallisation from isopropyl ether. When the enol form is complexed with chromium tricarbonyl, complete conversion to the keto form accelerated and occurs even at room temperature in benzene. In deoxyribonucleic acids (DNA), the nucleotide bases are in keto form. However, James Watson and Francis Crick first believed them to be in the enol tautomeric form, delaying the solution of the structure for several months.
from http://www.chemie.de/lexikon/e/Keto-enol_tautomerism
I don’t want to be technical. I just wanted to share a little of my knowledge about (for me) organic chemistry’s most fascinating lesson that could best describe what I am up right now. What do you think am I doing at two in the morning? I should be sleeping. Yes! I am a TAUTOMER. As a tautomer, I am trapped in a situation that I think hard to forget. The equilibrium constant between what I feel and what I should feel is very small. I don’t know if you understand it but let us put it in this way my feeling is somewhat inconvertible. Sometimes I think that I should leave the past behind but sometimes I can see old Edward reminiscing the past – until I found him in the cobweb of history.
Lent is very special to me because it keeps on reminding me to get away from the past and should continue leaving for the future –even though it is hard.
Keto-enol tautomerism is important in several areas of biochemistry. The high phosphate-transfer potential of phosphoenolpyruvate results from the fact that the phosphorylated compound is "trapped" in the less stable enol form, whereas after dephosphorylation it can assume the keto form. Rare enol tautomers of the bases guanine and thymine can lead to mutation because of their altered base-pairing properties.In certain aromatic compounds such as phenols the enol is important due to the aromatic character of the enol but not the keto form. Melting the naphthalene derivative 1,4-dihydroxynaphthalene 1 at 200 °C results in a 2:1 mixture with the keto form 2. Heating the keto form in benzene at 120°C for three days also affords a mixture (1:1 with first order reaction kinetics) The keto product is kinetically stable and reverts back to the enol in presence of a base. The keto form can be obtained in a pure form by stirring the keto form in triflic acid and toluene (1:9 ratio) followed recrystallisation from isopropyl ether. When the enol form is complexed with chromium tricarbonyl, complete conversion to the keto form accelerated and occurs even at room temperature in benzene. In deoxyribonucleic acids (DNA), the nucleotide bases are in keto form. However, James Watson and Francis Crick first believed them to be in the enol tautomeric form, delaying the solution of the structure for several months.
from http://www.chemie.de/lexikon/e/Keto-enol_tautomerism
I don’t want to be technical. I just wanted to share a little of my knowledge about (for me) organic chemistry’s most fascinating lesson that could best describe what I am up right now. What do you think am I doing at two in the morning? I should be sleeping. Yes! I am a TAUTOMER. As a tautomer, I am trapped in a situation that I think hard to forget. The equilibrium constant between what I feel and what I should feel is very small. I don’t know if you understand it but let us put it in this way my feeling is somewhat inconvertible. Sometimes I think that I should leave the past behind but sometimes I can see old Edward reminiscing the past – until I found him in the cobweb of history.
Lent is very special to me because it keeps on reminding me to get away from the past and should continue leaving for the future –even though it is hard.
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