Question

Briefly describe the molecular properties of the dimedone molecule that can be interpreted from the 1H NMR spectrum.

Answer 1

mis Dimedone :- Dimedone is a cyclic diketone wad in ooganic Chemistry to detamine weather a compound contains an Aldehyde group. structure: IUPAC Name - 5,5 dimethy) - cyclohexane 1,3 dione. properties :- olalar formula Cattoo. Apperence : yellow coystals. molar mass 140.17 mp 147 to 150c * Yoger and mazar have presented a detailed 60 Hz HNAR Spectral Strudy of the tautome nism of dimedone. In chlorofoom Solution, at very high dilution, the predominen Keto (diketo (4)) form was in equilibrium with the monomeric end forme (keto-enol, 3-hydroxy, sis dimethyl cyclohex 2-ene lone) as shown in (11). (1) 01 Keto form (11) 8 2 enol form. existed in * in the tab At higher concentrations the enol dimeric and polymeric forms. The H NMR Chemical shifts are given those mesured in CD cl solution. *

B. All the signals were singlets. irradiation of the 2-4 and 6-H enol signals indicated a lack of any significant allylic interaction between these nuclei. o from the respective CH₃ integrations the keto end - Comparision (1/2) ratio was determined as 66:36. Yogevand Mazur reported ratio of 59:41 fora 0.0969 solution at 10c. IN Dmso-do solution dimedone exist almost exclusively as the (II) form: although the minimal presence of I form was not evident in the H Spectrum. 1 270 MH3 H NMR spectra of dimedone: Chemical a 5.495 CoCl₂ DMSo-do em shift keto (I) Enol (1) Enol (II) 2-H 5.209 2-CH₂ 3.346 416-CH₂ 2.539 2.267 2.128 5-CH3 1.046 애 a observed tautomeric ratio Ketolenol 64:39, from CH3 integrals. 6 shift dependent on residual H₂O Concentration. 1.090 0.9913 10.56 11.ob