5- - 2,4-dihydroxybenzoic acid

Tropolone has been made from 1,2-cycloheptanedione by bromination and reduction, and by reaction with A -bromosuccinimide from cyolo-heptanone by bromination, hydrolysis, and reduction from diethyl pimelate by acyloin condensation and bromination from cyclo-heptatriene by permanganate oxidation from 3,5-dihydroxybenzoic acid by a multistep synthesis from 2,3-dimethoxybenzoic acid by a multistep synthesis from tropone by chlorination and hydrolysis, by amination with hydrazine and hydrolysis, or by photooxidation followed by reduction with thiourea from cyclopentadiene and tetra-fluoroethylene and from cyclopentadiene and dichloroketene. - ... 

Convert benzoic acid to 3,5-dihydroxybenzoic acid (alpha-resorcyclic acid) (I). 50 g (I), 134 g dimethylsulfate, 60 g NaOH, 300 ml water add 35 g NaOH and reflux to obtain about 50 g 3,5-dimethoxybenzoic acid (II) which is converted to dimethoxybenzoyl chloride (HI) with PCI5. Extract the (HI) with ether and filter. Saturate the ether with NH3 at 0° C and filter. Wash with ether and water and reciystallize from hot water to get 3,5-dimethoxy-benzamide (IV). To a solution of 1 M of n-hexyl bromide (or 1,2-dimethylheptyl bromide, etc.) add 24.3 g Mg in 200 ml ether to... 

Considerable attention has been paid to aromatic hyperbranched polyesters synthesized from monomers derived from 3,5-dihydroxybenzoic acid (DBA). The thermal stability of DBA is not good enough to allow direct esterification of DBA, and therefore chemical modifications are necessary. Some aromatic monomers used for the synthesis of hyperbranched aromatic polyesters are presented in Fig. 6. 

Dimethoxybenzaldehyde. (This can be purchased for a modest fee from chemical supply houses. If you prefer to use the "make your own" method of procurement see the procurement chapter, then follow the instructions below.) Aust. J. Chem. 21, 2979 (1968). Make a mixture of 50 g 3,5-dihydroxybenzoic acid, 200 ml dimethylsulfate, 250 g K2CO3, in one liter of acetone, and reflux for 4 hours. Distill the acetone off and extract the residue with 1 liter of ether. Wash the extracts with two 100 ml portions of coned ammonium hydroxide, two 100 ml portions of... 

Buy 3,5-dimethoxybenzoic acid or make like this. 3,5-dihydroxybenzoic acid is mixed with 134 g of dimethylsulfate, 60 g of sodium hydroxide, 300 ml and 35 g more sodium hydroxide, then reflux. This 3,5-dimethoxybenzoic acid is converted to 3,5-dimethoxybenzoyl chloride by reacting with PCI5, which is extracted with portions of ether and filter. Saturate the ether with ammonia, after cooling the ether to 0°, and filter. Wash the solids with cold ether, then water, and recrystallize from hot water to get 3,5-dimethoxybenzamide. 

Figure 6.4 Monitoring of electroosmosis stability during separation of derivatives of benzoic acid using a thermo-marker. TMl—first thermo-marker, TM2—second thermo-marker 1—aminobenzoic acid, 2— benzoic acid, 3—3,5-dihydroxybenzoic acid, 4—salicylic acid, 5—3,5-dinitrobenzoic acid. Background electrolyte 5 mM [C4CiIm][FAcO] in acetonitrile.

If the OH-groups of the guest become more acidic, e.g. upon changing the guest from resorcinol to 2,4-dibromoresorcinol, the increases from 2600 to 5600(Table 2, entries 2 and 3). In the case of 3,5-dihydroxybenzoic acid methyl ester, the value reaches the relatively high value of 35000 M" ... 

Dihydroxybenzoic acid is most conveniently prepared by alkaline fusion of the disulfonic acid obtained by sulfonation of benzoic acid.1,2,3 It has also been prepared by alkaline fusion... 

Products formed in the chlorination of humic acid and 3,5-dihydroxybenzoic acid (324). 

Fig. 6.24. Electrochromatographic separation of aromatic acids (a) and anilines (b) on monolithic capillary columns. (Reprinted with permission from [14]. Copyright 2000 Elsevier). Conditions monolithic poly(butyl methacrylate-co-ethylene dimethacrylate) stationary phase with 0.3 wt. % 2-acrylamido-2-methyl-l-propanesulfonic acid pore size, 750 nm UV detection at 215 nm voltage, 25 kV pressure in vials, 0.2 MPa injection, 5 kV for 3 s. (a) capillary column, 100 pm i.d. x 30 cm (25 cm active length) mobile phase, 60 40 vol./vol mixture of acetonitrile and 5 mmol/L phosphate buffer pH 2.4. Peaks 3,5-dihydroxybenzoic acid (1), 4-hydroxybenzoic acid (2), benzoic acid (3), 2-toluic acid (4), 4-chlorobenzoic acid (5), 4-bromobenzoic acid (6), 4-iodobenzoic acid (7). (b) capillary column, 100 pm i.d. x 28 cm (25 cm active length) mobile phase, 80 20 vol./vol mixture of acetonitrile and 10 mmol/L NaOH pH 12. Peaks 2-aminopyridine (1), 1,3,5-collidine (2), aniline (3), N-ethylaniline (4), N-butylaniline (5).

Frechet et al. 15 reported the high yield, one-step, reproducible preparation of the hyperbranched aromatic polyester (5) with controllable molecular weights via the selfcondensation of 3,5-bis(trimethylsiloxy)benzoyl chloride (6), which was synthesized from 3,5-dihydroxybenzoic acid by silylation (Me3SiCl, Et3N), followed by treatment with thionyl chloride and a catalytic amount of tetramethylammonium chloride. 

Turner, Voit, and Mourey 18,19 later reported analogous polyester hyperbranched macromolecules (5) via the thermal polymerization of A2B monomer 7 (Scheme 6.2). The diacetate was prepared by the treatment of 3,5-dihydroxybenzoic acid with acetic anhydride. 

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