Acidity aldehydes and ketones

There are actually three reactions called by the name Schmidt reaction, involving the addition of hydrazoic acid to carboxylic acids, aldehydes and ketones, and alcohols and alkenes. The most common is the reaction with carboxylic acids, illustrated above.Sulfuric acid is the most common catalyst, but Lewis acids have also been used. Good results are obtained for aliphatic R, especially for long chains. When R is aryl, the yields are variable, being best for sterically hindered compounds like mesi-toic acid. This method has the advantage over 18-13 and 18-14 that it is just one laboratory step from the acid to the amine, but conditions are more drastic. Under the acid conditions employed, the isocyanate is virtually never isolated. 

Hanssen, and Nair,127 and by Chadwick et a/.128 All deal with mono-, di-tri-, and sometimes tetra-substituted furans where the substituents are variously selected from halogen, ester, acid, aldehyde, and ketonic functions. Here we consider only some more special situations. 

Peters R, Hellenbrand J, Mengerink Y, Wal Van der S. 2004. On-line determination of carboxylic acids, aldehydes and ketones by high-performance liquid chromatography-diode array detection-atmospheric pressure chemical ionization mass spectrometry after derivatization with 2-nitrophenylhydrazine. J Chromatogr A 1031 35. 

Reiss, R., P. B. Ryan, S. J. Tibbetts, and P. Koutrakis, Measurement of Organic Acids, Aldehydes, and Ketones in Residential Environments and Their Relation to Ozone, J. Air Waste Manage. Assoc., 45, 811-822 (1995a). 

Symmetrical ethers are obtained from the dehydration of two molecules of alcohol with H2SO4 (see Section 5.5.3). Alcohols react with p-toluenesul-phonyl chloride (tosyl chloride, TsCl), also commonly known as sulphonyl chloride, in pyridine or EtsN to yield alkyl tosylates (see Section 5.5.3). Carboxylic acids, aldehydes and ketones are prepared by the oxidation of 1° and 2° alcohols (see Sections 5.7.9 and 5.7.10). Tertiary alcohols cannot undergo oxidation, because they have no hydrogen atoms attached to the oxygen bearing carbon atom. 

Singlet excited state acid dissociation constants pK can be smaller or greater than the ground state constant pK by as much as 8 units. Phenols, thiols and aromatic amines are stronger acids upon excitation, whereas carboxylic acids, aldehydes and ketones with lowest >(71, ) states become much more basic. Triplet state constants pKr are closer to those for the ground state. Forster s cycle may be used to determine A pK =pK —pK) from fluorescence measurements if proton transfer occurs within the lifetime of the excited molecule. 

Use of the resins with samples containing free chlorine residual is not recommended. Cheh (35) suggested that chlorine may produce mutagenic artifacts on XAD-4. Our experiment with 2-mg/L chlorine residual appeared to promote the release of irreversibly adsorbed spiked standards Six model compounds were recovered at levels several times higher than those observed in normal blank runs. In addition, many resin artifacts were eluted after exposure to this chlorine level, primarily aromatic and aliphatic acids, aldehydes, and ketones. Stoichiometric dechlorination (ferrous ion) is therefore recommended in order to avoid cross contamination between samples and inclusion of undesirable resin artifacts in the residue to be bioassayed. 

SCHMIDT REACTION. Acid catalyzed addition of hydrazonic acid to carboxylic acids, aldehydes, and ketones to give amines, nitriles, and amides, respectively. 

The carboxyl function does absorb ultraviolet radiation, but the wavelengths at which this occurs are appreciably shorter than for carbonyl compounds such as aldehydes and ketones, and, in fact, are out of the range of most commercial ultraviolet spectrometers. Some idea of how the hydroxyl substituent modifies the absorption properties of the carbonyl group in carboxylic acids can be seen from Table 18-2, in which are listed the wavelengths of maximum light absorption (Amax) and the extinction coefficients at maximum absorption (emax) of several carboxylic acids, aldehydes, and ketones. 

Wavelengths tor Maximum Ultraviolet Absorption of Some Carboxylic Acids, Aldehydes, and Ketones (n--- n )... 

Excluding carboxylic acids, aldehydes, and ketones (see appropriate sections). b Other isomers were formed, but were not isolated. 

Reiss, R., Ryan, P.B., Tibbetts, S. and Koutrakis, P. (1995b) Measurement of organic acids, aldehydes, and ketones in residential environments and their relation to ozone. Journal of the Air ej Waste Management Association, 45, 811-22. 

Aldehydes and organic acids Aldehydes and ketones determined directly, oxoacids converted to methyl esters with diazomethane [235]... 

In the presence of molecular oxygen, the oxidation of initially pure paraffins and cycloparaffins takes place at temperatures from 120 to 160 °C. In parallel with other products, there are formed acids, aldehydes, and ketones which induce the decomposition of hydroperoxides. This is documented by kinetic curves of hydroperoxide accumulation which show a maximum [78]. 

The ozonization of some a,j8-unsaturated acids, aldehydes, and ketones proceeds abnormally in the presence of water, the C—C bond adjacent to the carbonyl group being cleaved as well as the C—C double bond.8 Barton and Seoane123 formulated this reaction as formation of the ozonide, followed by decomposition by a concerted mechanism, in which water plays an important part see also Refs. 124 and 125. 

In a mure specific definition, the carbon atom introduced originates from synthesis gas (CO/Hj) in a homogeneously-catalyzed liquid phase reaction. Substrates accessible for homologation are, in particular, alcohols but can also be ethers, esters.acids, aldehydes, and ketones [1"6]. 

Similar to the cyanohydrin synthesis for hydroxy acids is the Strecker synthesis of amino acids. Aldehydes and ketones are converted to a-amino cyanides by ammonia and hydrogen cyanide or by aqueous ammonium chloride and sodium cyanide solutions. Amino cyanides may also be obtained by the action of gaseous ammonia on cyanohydrins (cf. method 391). The preparation of DL-alanine (60%) is typical. "... 

Figure 2 Schematic showing principle oxidation processes in the troposphere in NO -rich air (after Prinn, 1994). In NOj.-poor air (e.g., remote marine air), recychng of HO2 to OH is achieved hy reactions of O3 with HO2 or hy conversion of 2HO2 to H2O2 followed hy photodissociation of H2O2. In a more complete schematic, nonmethane hydrocarbons (RH) would also react with OH to form acids, aldehydes and ketones in...

Determination of the residual antioxidant content in polymers by HPLC and MAE is one way to determine the amoimt needed for reasonable stabilization of a material, and also to compare different antioxidants and their individual efficiencies. During ageing and oxidation of PE, carboxyhc acids, dicarboxylic acids, alcohols, ketones, aldehydes, n-alkanes and 1-alkenes are formed [86-89]. The carboxyhc acids are formed as a result of various reactions of alkoxy or peroxy radicals [90]. The oxidation of polyolefins is generally monitored by various analytical techniques. GC-MS analysis in combination with a selective extraction method is used to determine degradation products in plastics. ETIR enables the increase in carbonyls on a polymer chain, from carboxylic acids, dicarboxyhc acids, aldehydes, and ketones, to be monitored. It is regarded as one of the most definite spectroscopic methods for the quantification and identification of oxidation in materials, and it is used to quantify the oxidation of polymers [91-95]. Mechanical testing is a way to determine properties such as strength, stiffness and strain at break of polymeric materials. 

Intramolecular charge-transfer excited states may also arise from the promotion of a re-electron from the aromatic ring to a vacant re -orbital localized on an exocyclic group. This phenomenon is often observed in aromatic carboxylic acids, aldehydes, and ketones, where the carbonyl group is conjugated with the aromatic ring. 

Seeberger and co-workers [27] demonstrated a facile approach for the fluorination of alcohols, carboxylic acids, aldehydes, and ketones by harnessing the synthetic utility of diethylaminosulfur trifluoride (DAST) (37) in a PTFE flow reactor (reactor volume = 16.0 ml) maintained at 5 bar and 70 °C. 

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