Ketone cyclic, ring size

The combined action of carbon tetrachloride, trioctylphosphine and 7V,7V-dimethylani-line on Af-(hydroxymethyl)pyrrole in ether gives the salt 70 via unstable l-(chlor-omethyl)pyrrole (69). Addition of the morpholine enamines of cyclic ketones of ring size six, seven or eight to the salt affords mixtures of tricyclic derivatives 72 and 73 of pyrrole, which are thought to be formed via 5-azoniafulvene chloride 71 (equation 34)55. 

Some toxicological data for cyclic ketones are shown in Table 16. Interestingly, toxicity is shown to increase with ring size. This is in reverse order of relative reactivity. 

The formation of crystal inclusion of 47 and 48 with cyclic ketones of suitable ring size (cyclopentanone, cyclohexanone) and with cyclohexene oxide are also important facts. Corresponding inclusion compounds with alcohols or amines could not be obtained. With reference to the heterocyclic guest molecules, the suitability of the ring size is likely to be the decisive factor for guest inclusion. 

Aliphatic c a -dibromo ketones, such as 2,4-dibromopentan-3-one (262), react with primary amines RNH2 (R = Me, Et, Pr, /-Pr or t-Bu) to give mixtures of imines 263 and lesser amounts of diimines 264. l,3-Dibromo-l-phenylpropan-2-one yields only the amide 265, the product of a Favorskii rearrangement. The nature of the products from aliphatic amines and cyclic a,a -dibromo ketones depends on ring size the cyclohexanone derivative 266 gave Favorskii amides 267 (R = Pr, /-Pr or t-Bu), while trans-2,5-dibromocyclopentanone afforded the enamines 268 (R = /-Pr or t-Bu) (equation 95)296. 

Exercise 23-30 The following sequence is very useful for expanding the ring size of a cyclic ketone ... 

It may be of interest to compare the photochemistry of the unsubstituted cyclic ketones. The effect of ring size on the ultraviolet absorption spectrum has been discussed (4,22) although its pertinence to the photochemistry is not obvious. 

In contrast, aromatic ketones are high boiling, colorless liquids that generally have a fragrant odor and are almost insoluble in water. They are useful as intermediates in chemical manufacture. Functionalized and cyclic ketones are also good solvents. Ring size and the type and location of functional groups affect odor, color, and reactivity of these ketones. 

The chemical properties of cyclic ketones also vary with ring size. Lower members (addition reactions, than corresponding acyclic ketones. The Cg—C12 ketones are unreactive, reflecting the strain and high enol content of medium-sized ring systems. Lactones are prepared from cyclic ketones by the Bayer-Villiger oxidation reaction with peracids. S-Caprolactone is manufactured from cyclohexane by this process ... 

An effect of the ring-size in addition to that observed in the elimination taking place in the reduction of vicinal dibromides, has been observed for medium-sized ring compounds which carry the electro-active group either in the side-chain or directly attached to the ring. The half-wave potentials of cycloalkyl bromides can be correlated with the half-wave potentials of cyclic ketones and their derivatives (Fig. 29). The observed relation indicates that the relative effect of ring-size on the reactivity is similar in all the reaction series compared. 

Using methods similar to Fischer s, the straight-chain form of any monosaccharide can be worked out. As we have seen, however, monosaccharides exist mostly as cyclic pyra-nose or furanose hemiacetals. These hemiacetals are in equilibrium with the open-chain forms, so sugars can react like hemiacetals or like ketones and aldehydes. How can we freeze this equilibrium and determine the optimum ring size for any given sugar Sir Walter Haworth (inventor of the Haworth projection) used some simple chemistry to determine the pyranose structure of glucose in 1926. 

However, cyclic ketones can themselves be decarbony-lated by [RhCl(PPh3)3] in high-boiling solvents. There appears to be no correlation with ring size since both 3-hexadecylcyclobutanone and cyclododecanone can be decarbonylated. ... 

Reaction of alkylidene cycloalkanes (399) with cyanogen azide (400) (64JA4506), followed by hydrolysis, affords ring-expanded cyclic ketones (401), a reaction applicable to a wide variety of ring sizes and to both saturated and a,/S- unsaturated ketones (69JA3676,73joc282i). 

The exact position of the carbonyl absorption often provides additional information about a compound. For example, most aldehydes have a C=0 peak around 1730 cm , whereas for ketones, it is typically around 1715 cm . Two other structural features—ring size (for cyclic ketones) and conjugation—affect the location of the carbonyl absorption in a predictable manner. 

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