P-Methylbenzaldehyde

In the Gatteinicin-Koch reaction, a formyl group (-CHO) is introduced directly onto a benzene ring. For example, reaction of toluene wjfh CO and HCJ in the presence of mixed CUCI/AICI3 gives p-methylbenzaldehyde. Propose a mechanism. 

Benzenediamine (352) and 4-p-chlorobenzyl-3-hydroxy-5-p-tolyl-2,5-dihy-dro-2-furanone (353) gave 3-(p-chlorophenethyl)-2(177)-quinoxahnone (354) with loss of p-methylbenzaldehyde (isolated as its phenyUiydrazone) (EtOH,... 

The generation of phenylcarbene (512) and p-tolylcarbene at 250 °C/40Torr in the gas phase brought about only the ring expansion to give 5 and 10, respectively and their dimerization yielding 522 and 557 (Scheme 6.113). The co-thermolysis of the sodium salts of benzaldehyde and p-methylbenzaldehyde tosylhydrazone also gave rise to the mixed heptafulvalene 556. With a ratio of 1 2 1, the amounts of 522, 556 and 557 verified the expectation based on statistics [212]. 

Scheme 6.113 Formation of heptafulvalene (522), its methyl derivative 556 and its dimethyl derivatives 557 on co-thermolysis of the sodium salts of benzaldehyde and p-methylbenzaldehyde tosylhydrazones.

Photolytic. A n-hexane solution containing /n-xylene and spread as a thin film (4 mm) on cold water (10 °C) was irradiated by a mercury medium pressure lamp. In 3 h, 18.5% of the p-xylene photooxidized into p-methylbenzaldehyde, p-benzyl alcohol, p-benzoic acid, and p-methylacetophenone (Moza and Feicht, 1989). Glyoxal and methylglyoxal were produced from the photooxidation of p-xylene by OH radicals in air at 25 °C (Tuazon et al., 1986a). The rate constant for the reaction of p-xylene and OH radicals at room temperature was 1.22 x lO " cmVmolecule-sec (Hansen et al., 1975). A rate constant of 7.45 x 10 L/molecule-sec was reported for the reaction of p-xylene with OH radicals in the gas phase (Darnall et al, 1976). Similarly, a room temperature rate constant of 1.41 x 10 " cm /molecule-sec was reported for the vapor-phase reaction of p-xylene with OH radicals (Atkinson, 1985). At 25 °C, a rate constant of 1.29 x lO " cmVmolecule-sec was reported for the same reaction (Ohta and Ohyama, 1985). 

Arnett and coworkers later examined the reaction of lithium pinacolone enoiate with substituted benzaldehydes in THE at 25 °C. The determination of the heat of reaction indicated that the Hammett p value for the process is 331. Although the aldol reaction was instantaneous in THF at 25 °C, the reaction with o- or p-methylbenzaldehyde could be followed using a rapid injection NMR method in methylcyclohexane solvent at —80 °C. Application of Eberson s criterion based on the Marcus equation, which relates the free energy of ET determined electrochemically and the free energy of activation determined by kinetics, revealed that the barriers for the ET mechanism should be unacceptably high. They concluded that the reaction proceeds via the polar mechanism . Consistent with the polar mechanism, cyclizable probe experiments were negative . The mechanistic discrepancy between the reactions of benzaldehyde and benzophenone was later solved by carbon kinetic isotope effect study vide infraf. ... 

Problem 15.18 Prepare the following compounds from benzene, toluene, and alcohols of four or fewer C s (a) 2-methylpropanal (isobutyraldehyde), (b) p-chlorobenzaldehyde, (c) p-nitrobenzophenone (p-NOjCftH4COC,.H,), (d) benzyl methyl ketone, (e) p-methylbenzaldehyde. ... 

When a slurry mixture of p-methylbenzaldehyde lb (1.5 g, 12.5 mmol), acetophenone 2b (1.5 g, 12.5 mmol) and NaOH (0.5 g, 12.5 mmol) was ground by pestle and mortar at room temperature for 5 min, the mixture turned to a pale yellow solid. The solid was combined with water and filtered to give p-methyl-chalcone 3b (2.7 g) in 97% yield. 

Condensations of erythritol with benzaldehyde,78,78 o-, wi-andp-chloro-benzaldehyde,18 p-methylbenzaldehyde,18 p-methoxybenzaldehyde,18 o-, m- and p-nitrobenzaldehyde,18,87 3-nitro-4-chlorobenzaldehyde,18 acetaldehyde,74 chloroacetaldehyde,74 acetone,1718 formaldehyde,78 and val-eraldehyde76 have been reported, but in no case has the structure of the product been determined. The physical constants of these acetals and ketals are recorded in Table VII. The photo-sensitivity of o-nitrobenzyl-idene-erythritols has been discussed on page 149. 

Rate Constants for the Oxidation of Benzaldehyde and p-Methylbenzaldehyde in Polyoxyethylene(24) Hexadecanol at 25° ... 

Certain aromatic and heterocyclic olefinic esters ate best prepared by condensation of ethyl acetate and aromatic aldehydes by sodium sand (Claisen). Benzaldehyde in this reaction gives ethyl cinnamate, C,HsCH=CHC03C,H5 (74%). p-Methylbenzaldehyde, furfural, furylactolein, and 2-thiophenecarboxaldehyde have been condensed in a similar manner. 

Problem 28.5 When p-methylbenzyl hydroperoxide, P-CH3C6H4CH2O—OH, is treated with acid, there are obtained p-methylbenzaldehyde (61%) and p-cresol (38%). (a) How do you account for the formation of each of these What other products must have been formed (b) What do the relative yields of the aromatic products show ... 

Table 7. Electroreductions of Benzaldehyde, p-Methylbenzaldehyde, Dimethylmaleate, and Benzyl Bromide3...

Industrially, terephthalic acid is produced by the cobalt(III) acetate, manganese(III) acetate, or ammonium molybdate-catalyzed air oxidation of />-xylene in acetic acid. Sodium bromide reduces the induction period and increases the rate of conversion to terephthalic acid. p-Xylene is initially oxidized to p-methylbenzyl hydroperoxide, and further oxidation gives p-methylbenzaldehyde and p-methylbenzoic acid ... 

Terephthalic acid is not formed until p-methylbenzaldehyde has been completely converted to p-methylbenzoic acid. 

The cuiTent process for producing aromatic and aliphatic aldehydes by direct hydrogenation of the corresponding carboxylic acids over Zr02 and Cr203 has been developed by the Mitsubishi Chemical Corporation. It has successfully commercialized the production of p-t-butylbenzaldehyde, m-phenoxybenzaldehyde, p-methylbenzaldehyde, 10-undecenal, and dodecanal by reduction of the corresponding acids. By use of this technology, ca. 2000 t y of aldehydes have been manufactured since 1988 [3]. 

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