Aldehydes infrared absorptions

Table 19.2 I Infrared Absorptions of Some Aldehydes and Ketones...

Catalytic dehydrogenation of alcohol is an important process for the production of aldehyde and ketone (1). The majority of these dehydrogenation processes occur at the hquid-metal interface. The liquid phase catalytic reaction presents a challenge for identifying reaction intermediates and reaction pathways due to the strong overlapping infrared absorption of the solvent molecules. The objective of this study is to explore the feasibility of photocatalytic alcohol dehydrogenation. 

The catalyst formed in this manner exhibited carbonyl infrared absorptions, as shown in Table XXX. These catalysts were tested by hydroformylation of ethylene or propylene at 100°C and atmospheric pressure. Both were effective, with (A) being better than (B), probably because of the higher surface area. The aldehyde formed from propylene was a mixture of 63% n- and 37% isobutyraldehyde. The rate expression for ethylene hydroformylation was ... 

There is no report of the boiling point of the product in the literature.3 The product has an infrared absorption (CC14 solution) at 1732 cm.-1 (aldehyde C=0). 

When the extract is passed over an anion-exchange resin, approximately 40-45 percent of the solids are retained on the resin and the remainder passes through. Infrared absorption spectra of the two fractions are presented in Figure 3. The neutral fraction shows absorption of infrared at 3 microns (hydroxyl), 5.9 microns (aldehydic carbonyl), and at 9-10 microns (C-O-C and C-O-H), with little absorption at 3.4 microns (C-H stretch). This spectrum resembles that of the common simple sugars when scanned as a melt between NaCl optics. 

Figure 5. Infrared absorption spectra of the acidic furnish extract fraction fractionated further by sequential extraction into aldehydic (bisulfite), hydroxyl (bicarbonate), phenolic (hydroxide), and aliphatic (neutral residual) fractions...

Identification The infrared absorption spectrum of the sample exhibits relative maxima at the same wavelengths as those of a typical spectrum as shown in the section on Infrared Spectra, using the same test conditions as specified therein. Assay Not less than 80.0%, by volume, of total aldehydes. Angular Rotation Between -1° and +1°. 

The hydrogen-bonding group of each polymer has been taken as equivalent to that of the parent mononrer. (The hydrogen-bonding tendency can be assigned qualitatively in the order alcohols > ethers > ketones > aldehydes > esters > hydrocarbons or setniquantitatively from infrared absorption shifts of CH rOD in a reference solvent and in the liquid of interest (7J.)... 

The infrared absorption spectra of these compounds showed, however, that the compounds do not have the structure of type IV, but that the structure is in fact of the aldehyde-amine, addition type (V) that is, the compounds are analogous to aldehyde-ammonia compounds. The expected... 

Pinchas, S. (1955) Infrared absorption of the aldehydic C-H group. Anal. Chem. 27, 2-6. 

To ensure that photolysis is the only loss process for the aldehyde experiments can be carried out in the presence of an excess concentration of a radical scavenger such as cyclohexane. In cases where the high concentration of a scavenger is undesirable, e.g. because it causes saturation in the infrared absorption spectrum, a tracer compound, such as di-n butyl ether, can be used to correct for the measured decay of the aldehyde in order to obtain the j value. Typical starting concentrations used in photolysis experiments at EUPHORE are [aldehyde] = 0.5-1.5 ppmv, [scavenger] = 10-50 ppmv or [tracer] = 0.1-02. ppmv (Wenger et ai, 2004 and Magneron et al, 2002). 

In a similar investigation on the deoxy derivative (33) of iSr,Ar -dibenzoyl-streptamine, Folkers and coworkers isolated a crystalline dialdehyde compound which is, accordingly, 2,4-dibenzamido-2,4,5-trideoxy-a t/io-hexodialdose (34). The compound showed no aldehyde carbonyl absorption in its infrared spectrum and was, therefore, assigned a cyclic structure. It gave a crystalline bis(diethyl dithioacetal). 

---