Ethyl acetate structure

However, since it is not easy to explain the formation of acetic anhydride from I, Bawn and Williamson [9] proposed a hydroperoxidic hydro-peroxy-1-ethyl acetate structure whose formation involves the anion HOj, viz. 

Dinitro- and trinitrophenanthrenes were fiactionated using NP techniques. Cmde dinitrophenanthrene products were collected in nine fractions using a silica colunm (A = 280 nm) and 50/50 hexane/dichloromethane as a mobile phase [631]. A rapid change to 70/20/10 hexane/dichloromethane/ethyl acetate eluted a tenth fraction. Elution was complete in <20 min. Similar techni es were used for the trinitrophenanthrenes. Further fiactionation was carried out on late eluting collected fiactions using different mobile phases such as 60/35/5 hexane/dichloromethane/ethyl acetate. Structural confirmation was done GC/MS. 

Figure 20 1 shows the structures of various derivatives of acetic acid (acetyl chlo ride acetic anhydride ethyl thioacetate ethyl acetate and acetamide) arranged m order... 

NMR Chemical shift differences m their H NMR spectra aid the structure deter mmation of esters Consider the two isomeric esters ethyl acetate and methyl propanoate As Figure 20 9 shows the number of signals and their multiplicities are the same for both esters Both have a methyl singlet and a triplet-quartet pattern for their ethyl group... 

From the point of view of solute interaction with the structure of the surface, it is now very complex indeed. In contrast to the less polar or dispersive solvents, the character of the interactive surface will be modified dramatically as the concentration of the polar solvent ranges from 0 to l%w/v. However, above l%w/v, the surface will be modified more subtly, allowing a more controlled adjustment of the interactive nature of the surface It would appear that multi-layer adsorption would also be feasible. For example, the second layer of ethyl acetate might have an absorbed layer of the dispersive solvent n-heptane on it. However, any subsequent solvent layers that may be generated will be situated further and further from the silica surface and are likely to be very weakly held and sparse in nature. Under such circumstances their presence, if in fact real, may have little impact on solute retention. 

Heat-treatment the active fractions from step 1 are combined and evaporated to a small volume ( 4ml), and mixed with a 1/4 volume of 1 M H3PO4. The mixture is heated in a bath of boiling water for 2 minutes, then quickly cooled. The precipitate formed is removed by centrifugation. The panal in the clear solution is extracted with ethyl acetate, and the extract is evaporated to dryness. The residue is redissolved in 30% methanol. During this process, the hydrated form of panal is converted into its basic structure. 

Properties of panal (Nakamura etal., 1988a). Purified panal is a colorless, amorphous solid, soluble in alcohols, water, ethyl acetate, and chloroform. The absorption spectrum (Fig. 9.3) shows a single peak (A.max 217nm, e 15,300). Optical rotation [a]D —17° (c 0.9, methanol). Mass spectrometry and NMR analysis showed that panal is a sesquiterpene aldehyde, C15H18O5 (Mr 278.30), with the structure shown below. 

One of the most dramatic examples of a solvent effect on propagation taken from the early literature is for vinyl acetate polymerization.78,79 Kamachi el al.n reported a ca. 80-fold reduction in kp (30aC) on shifting from ethyl acetate to benzonilrile solvent (Table 8.1). Effects on polymer structure were also reported. Hatada ef a m conducted a H NMR study on the structure of the PVAc formed in various solvents. They found that PVAc (M n 20000) produced in ethyl acetate solvent has 0.7 branches/chain while that formed in aromatic solvents is essentially unbranched. 

RbP02p2 and CSPO2F2 have comparable structural parameters ) E = ethyl acetate... 

This procedure was compared with sequential extractive techniques employing alkaline hydrolysis of dried plant tissue followed by extraction of the acidified mixture with ethyl acetate. Fractions were individually evaluated for phytotoxic properties. Selected fractions from those showing a positive response were analyzed by gas-liquid chromatography. Structural identification and characterization of the individual components in these selected fractions were accomplished by gas chromatography-mass spectrometry. 

A similar procedure was used to separate efficiently between cyclohexanol (b.p. 161 °C) and cyclohexanone (b.p. 155 °C), two structurally similar but chemically different species, by selective crystalline complexation with host 25 50). For example, when a solution of this host and a 1 1 mixture of the two guests in ethyl acetate was kept at room temperature for 24 hours, and the colorless crystals thus obtained were subsequently heated in vacuum, the composition of the resulting guest mixture was 94.71% of cyclohexanol and 5.23% of cyclohexanone. 

On intuition, a minute amount of water was added to the solvent (ethyl acetate) in the first crystallization experiment containing a molar excess of imidazole corresponding to 1, Regularly shaped crystals were formed within one hour. Such a crystal, subjected to X-ray analysis, has the structure as shown in Fig. 41 U1). Apart from the formation of the expected salt-type associate (carboxylate-imidazolium ion pair, cf. Sect. 4.2.2), two water molecules are present in the asymmetric unit of the crystal structure. This fact called our attention again to the family of serine protease enzymes, where water molecules are reported as being located in the close vicinity of the active sites 115-120),... 

In 1979 the bieyclic diol exo-2,ejco-6-dihydroxy-2,6-dimethylbicyclo[3.3.1]nonane (i) was prepared and observed to co-crystallise with various solvents, including ethyl acetate, chloroform, toluene, dioxane, and acetone. A crystal structure determination of the ethyl acetate compound revealed the occurrence of a helical canal host structure, containing ethyl acetate as guest (with 3 1 diol ethyl acetate stoichiometry), and that spontaneous resolution had occurred on crystallisation of the multimolecular inclusion compound 6>. 

If the C3-C7 separation of 1 is reduced by introduction of a smaller CH2 bridge, that is the dimethyl adamantanediol, 2,6-dihydroxy-2,6-dimethyltricyclo[3.3.1.1 3,7>]-decane (4), the host crystallises from ethyl acetate with a different, non-including, layer structure. The layers are comprised of orthogonal kinked strands as shown diagrammatically in Fig. 4(a), with the molecules connected along the strands and between the strands by cycles of four hydrogen bonds, as in Scheme 2. 

Fluconazole was shown to be crystallizable in the form of a monohydrate and as a 1/4 ethyl acetate solvate, as well as a new nonsolvated form [56], In the hydrate phase the water molecules were established as isolated sites, while the ethyl acetate molecules occupied constricted channels in its phase. In all of the structures, the fluconazole molecule adopted a common overall conformation, but one that was capable of some degree of flexibility. Hydrogen-bonding effects were deduced to be dominant in determining the structure of the different solvatomorphs. 

The formation of niclosamide hydrates, and the effect of relative humidity on the solvatomorphs obtained from acetone and ethyl acetate has been studied [79], The acetone and ethyl acetate solvatomorphs could be desolvated, and exposure to elevated humidity resulted in the formation of two hydrate structures. Each hydrate could be dehydrated into a different anhydrate phase, but only the hydrate formed from the acetone desolvate could be rehydrated to form a hydrate phase. Dynamic vapor sorption has been used to develop a method for determining the onset relative humidity of a glass transition and associated crystallization process [80]. 

Treatment of an ethyl acetate solution of the 5-aminoimidazole (96 R1 = Me, R2 = S02Me) with p-nitrobenzaldehyde in the presence of trifluo-roacetic acid gave a crystalline product, which was assigned the tricyclic structure (176) on the basis of spectral data [82IJC(B) 1087]. 

A solution of 5-0-(3-benzoylpropionyl)-3-deoxy-3-bromomethyl-l,2-di-O-acetyl-D-ribofuranose (2.35 g, 4.89 mmol) in triisopropyl phosphite (17 g, 81 mmol) was heated at 160 to 180°C with exclusion of moisture for 72 h. Volatile materials were removed under reduced pressure, and the residue was purified by chromatography on a silica gel column (48 x 2.7 cm) eluting with chloroform ethyl acetate (1 1). From the 150 to 500 ml eluent, there was isolated the pure 5-(3-benzoylpropionyl)-3-deoxy-3-diisopropoxyphosphinylmethyl-l,2-di-O-acetyl-D-ribofuranose (1.73 g, 68%) as an oil that exhibited IR and NMR spectra and analyses in accord with the proposed structure. 

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