Carbonyls groups

The trends in Table 2.31 illustrate that the carbonyl group obeys trends much like the simpler hydrides. As the basis set becomes more flexible, the interaction energy is lowered and the intermolecular distance lengthened. Much of this trend is due to the reduction 

The details of the optimized geometries of 1 and 11 are compared in Table 2.32, where it may be seen that the interoxygen distance is shorter in II, but the distance from the bridg- 

Dimitrova and Peyerimhoff focused their work on geometry I and helped provide a more accurate assessment of its interaction energy. Their highest level of theory stopped at MP2 but incorporated a 6-311 -t- H-G(2d,2p) basis set. The SCF part of the interaction energy is —4.79 kcal/mol, reduced to —4.04 when corrected for BSSE. The superposition-corrected contribution from MP2 correlation is —0.97 kcal/mol, adding up to a value of AE jec = 5.0 kcal/mol, quite similar to the best estimates for the water dimer. When zero-point vibrational corrections are added, this quantity lowers in magnitude to —3.3 kcal/mol. 

Ramelot et al. probed the nature of the minimum with the highest level of correlation to date, fully optimizing the geometries of stationary points. They verify the nature of structure II as a true minimum. At their highest level of theory, CCSD with a doubly-polarized 

A recent set of IR spectra in the gas phase suggest that the interaction energy is not very sensitive to substitution on the carbon atom. The measured interaction energies of HCl v/ith acetone, 2-butanone, methyl formate, and methyl acetate are all within 0.5 kcal/mol of one another. 

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A white solid, m.p. 178 C. Primarily of interest as a brominaling agent which will replace activated hydrogen atoms in benzylic or allylic positions, and also those on a carbon atom a to a carbonyl group. Activating influences can produce nuclear substitution in a benzene ring and certain heterocyclic compounds also used in the oxidation of secondary alcohols to ketones. 

Hammen equation A correlation between the structure and reactivity in the side chain derivatives of aromatic compounds. Its derivation follows from many comparisons between rate constants for various reactions and the equilibrium constants for other reactions, or other functions of molecules which can be measured (e g. the i.r. carbonyl group stretching frequency). For example the dissociation constants of a series of para substituted (O2N —, MeO —, Cl —, etc.) benzoic acids correlate with the rate constant k for the alkaline hydrolysis of para substituted benzyl chlorides. If log Kq is plotted against log k, the data fall on a straight line. Similar results are obtained for meta substituted derivatives but not for orthosubstituted derivatives. 

They are stable compounds and are not decomposed by dilute acids or alkalis. They are frequently employed in synthetic organic chemistry for protecting the carbonyl group. 

Simple stable carbonyls, except V(CO)o, have an electronic configuration corresponding to the next noble gas. Carbonyl groups can be substituted by other unchanged ligands (e.g. 

Figure C2.3.9. Product distribution of dissymmetrical ketone photolysis as influenced by cefyltrimethylammonium chloride (CTAC) micelles. The initial ketone, A(CO)B is photolysed to lose the carbonyl group and to produce tliree products, AA, AB and BB. These data are for benzyl (A) 4-methylbenzyl (B) ketone. Product AA is 1,2-diphenylethane, product BB is 1,2-ditolylethane and product AB is l-phenyl-2-tolyl-ethane. At low CTAC concentration, in the absence of micelles, a random distribution of products is obtained. In the presence of micelles, however, the AB product is heavily favoured. Adapted with pennission from 1571.

Hydroxylamine condenses with the carbonyl group of an aldehyde or ketone to form an oxime ... 

Hydrazine and its alkylated derivatives are used as rocket fuels in organic chemistry, substituted phenylhydrazines are important in the characterisation of sugars and other compounds, for example aldehydes and ketones containing the carbonyl group C=0. 

The tetrafluorides of the elements can be prepared. They are all less stable than the corresponding hexafluorides and are hydrolysed readily by water. They can all be used as fluorinating agents and sulphur tetrafluoride is extensively used for this purpose, for example the fluorination of organic carbonyl groups ... 

The aim of the second example is to find suitable reaction conditions for running the same reduction reaction as in the first example, but in the presence of another carbonyl group which should not react. Furthermore, the reaction should lead to a product with a yield of 80% or more and a specific stereochemical configuration. 

This oxidation proceeds readily if the methylene group is activated by linkage to (a) a carbonyl group, (b) an aromatic ring (c) an olefine link also activates adjacent CH2 and CH groups. 

When camphor (I) is heated with selenium dioxide in acetic acid, the methylene group next to the carbonyl group is oxidised also to a carbonyl group, to form camphorquinone (II). Note that the compound (II) is not a true quinone but a 1,2-diketone ... 

The mechanism of the reduction remains uncertain. The work of E. D. Williams, K. A. Krieger and A. R. Day (1953) using deuterium-labelled aluminium isopropoxide, shows that hydrogen atoms are transferred predominantly from the central carbon atom of an isopropoxide group to the carbon atom of the carbonyl group undergoing reduction, the process probably involving a cyclic complex ... 

Reagent A is particularly useful for the treatment of the lower aliphatic aldehydes and ketones which are soluble in water cf. acetaldehyde, p. 342 acetone, p. 346). The Recent is a very dilute solution of the dinitrophenylhydrazine, and therefore is used more to detect the presence of a carbonyl group in a compound than to isolate sufficient of the hydrazone for effective recrystallisation and melting-point determination. 

The role of the base is apparently primarily that of a proton remover from the reactive methylene group thus if B represents the base, reaction (i) gives the carbanion, which then combines with the positive carbon of the carbonyl group (reaction ii) the product regains a proton from the piperidinium ion, and then by loss of water followed by mono-decarboxylation of the malonic acid residue gives the final acid. 

Coulombic Terms. Coulombie energy of interaetion arises from permanent dipoles within the molecule to be modeled, for example, the partial - - and — charges within a carbonyl group... 

The Grignard reagent RMgX is nucleophilic by virtue of the potential car banion (alkyl anion) R. It will react with the electrophilic carbonyl group as follows ... 

The following reactions are characteristic of aliphatic aldehydes those which are shared by ketones, due to the presence of the carbonyl group, are given under Aliphatic Ketones (Section 111,74). 

By the ketonic hydrolysis of substituted acetoacetic esters this is brought about by the action of dilute alkali in the cold, followed by acidification and boiling. The free substituted acetoacetic acid is produced, which readily undergoes decarboxylation (since it has a carboxyl and a carbonyl group on the same carbon atom) to give a ketone, for example ... 

Most of the characteristic reactions of ketones (RR CO) depend upon condensation with substituted amines. The reactions occur between the carbonyl group and the —NHj group of the substituted amine, and hence are also shared by aldehydes RHCO ... 

By treatment of an amide with sodium hypobromite or sodium hypochlorite solution (or with the halogen and alkali), the amine of one less carbon atom is produced, the net result being the elimination of the carbonyl group. An example is ... 

With concentrated alkali, fission occurs at the position adjacent to the carbonyl group to give acetic acid and a mono-substituted acetic acid the process is termed acid hydrolysis. 

It should be noted that the Friedel-Crafts acylation differs from the Friedel-Crafts alkylation (compare Sections IV,3-4 and discussion preceding Section IV,1) in one important respect. The alkylation requires catal3d.ic quantities of aluminium chloride, but for acylation a molecular equivalent of aluminium chloride is necessary for each carbonyl group present in the acylating agent. This is because aluminium chloride is capable of forming rather stable complexes with the carbonyl group these complexes probably possess an oxonium... 

CgHjCOCHj + SeOa —> CgHgCOCHO + Se + H O This is one example of the oxidation by selenium dioxide of compounds containing a methylene group adjacent to a carbonyl group to thecorresponding a-ketoaldehyde or a-diketone (see also Section VII,23). 

Lithium aluminium hydride LiAlH is a useful and conveuient reagent for the selective reduction of the carbonyl group and of various other polar functional groups. It is obtained by treatment of finely powdered lithium hydride with an ethereal solution of anhydrous aluminium chloride ... 

Ketones or aldehydes possessing a —CH—, —CHj—, or —CHj group adjacent to the carbonyl group. 

The Stobbe condensation thus provides a method for introducing a propionic acid residue at the site of a carbonyl group. 

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