Fluorinated benzoic acids

Fig. 33 Examples of supramolecular rod4ike mesogens formed by self assembly of fluorinated benzoic acid and a /ra s-4-RF-cyclohexane carboxylic acid ( / / C) [120, 122]...

Fig. 34 Examples of supramolecular rod-like mesogens formed by self assembly of branched fluorinated benzoic acid into dimers and their 4,4 -bipyridine complexes (77° C) [166]...

An analytical method for ultra-trace determination (down to 0.1 4g/L) of 15 fluorinated aromatic carboxylic acids, used as water tracers, was described [290]. The method comprised off-line extraction of the acids with Isolute ENV-f at pH 1. 5, elution with acetonitrile, and GC-MS quantification. The examination of the behavior of the fluorinated benzoic acids on the hypercrosslinked extracting material showed that with increasing acidity the breakthrough volume of the acid decreases, while increasing its molecular size increases the breakthrough volume because of more effective dispersion interactions with sorbent material. 

The reaction of 2-arylbenzoxazoles with Al-chlorosuccinimide in the presence of a palladium catalyst yields the chlorinated product (4). However, in the related ace-toxylation process, the reaction occurs at the position ortho to nitrogen in the aryl ring and involves a palladated intermediate. The palladium-catalysed reaction of Al-arylamides with Al-fluoro-2,4,6-trimethylpyridinium triflate, a source of F, results in selective ortho-fluorination and may lead to mono- or di-fluorinated benzoic acids. Here, (5) is a likely intermediate. A review of selectivity in electtophilic Auorinations has been published. ... 

Thirteen fluorinated benzoic acids (e.g., 2-fluoro-, 2,6-difluoro-, 2,4,5-trifluoro-, 4-[trifluoromethyl]benzoic acid) were well resolved on a 35°C C g column (A = 270 ran) using an 84/16 (hold 7 min) ->20/80 (at 8 min hold 3 min) water (5mM phosphate at pH 4.3)/acetonitrile gradient [894]. Linear curves were... 

By contrast, the COOH group is lost in the Rh(I)-catalyzed conjugate addition of 2,6-diflu-orinated benzoic acids to electron-poor olefins (Michael acceptors Scheme 22.7) [13]. Alkyl acrylates and A,iV-dimethylacrylamide have been found to give higher yields than methyl vinyl ketone [13], The use of aqueous toluene as the solvent avoids the formation of the Mizoroki-Heck-type product, whereby the reaction has thus far only been applied to fluorinated benzoic acids 5 [13],... 

SCHEME 22.7 Rhodium-mediated decarboxylative conjugate addition of fluorinated benzoic acids. 

Sun, Z.-M., Zhao, P. (2009). Rhodium-mediated decarboxylative conjugate addition of fluorinated benzoic acids stoichiometric and catalytic transformations. Angewandte Chemie International Edition, 48, 6726-6730. 

By using 8-aminoquinoline benzamide substrates and picolinic acid auxiliaries as the directing groups, the Daugulis group reported a novel method for selective mono- or di-fluorination of arene and heteroarene C—H bonds. AgF was used as fluoride source and DMF, pyridine, or DMPU as solvent. This Cu-promoted C—H activation method shows excellent functional group tolerance and provides a straightforward way for the preparation of ortto-fluorinated benzoic acids (Scheme 9.14). ... 

There is little information for fluoro-substituted sulfinyl groups. Values of a and ffp for SOCFj based on benzoic acid ionization are 0.63 and 0.69 respectively , compared with values of about 0.52 and 0.49 for SOMe (Table 3). Thus the electronegative fluorine somewhat enhances the electron-attracting influence of the sulfinyl function and makes the order more definitely sulfur lone pair to engage in 7t(pp) conjugation. Values of and ffp for SOCF3 based on anilinium ion dissociation are 0.76 and 1.05 respectively . An increase of 0.13 as between and [Pg.509]

Methanol, ethanol and 3-methylbutanol [1], acetaldehyde, trichloroacetaldehyde [2] and acetone [3] all ignite in contact with gaseous fluorine. Lactic acid, benzoic acid and salicylic acid ignite, while gallic acid becomes incandescent. Ethyl acetate and methyl borate ignite in fluorine [2],... 

The obtained A 7 a() value and the energy equivalent of the calorimeter, e, are then used to calculate the energy change associated with the isothermal bomb process, AE/mp. Conversion of AE/ibp to the standard state, and subtraction from A f/jgp of the thermal corrections due to secondary reactions, finally yield Ac f/°(298.15 K). The energy equivalent of the calorimeter, e, is obtained by electrical calibration or, most commonly, by combustion of benzoic acid in oxygen [110,111,113]. The reduction of fluorine bomb calorimetric data to the standard state was discussed by Hubbard and co-workers [110,111]. 

The fluorination of other activated aromatic compounds, such as anisole and phenol, undergo monofluorination mainly in the ortho and para positions, whereas the fluorination of deactivated aromatics, such as nitrobenzene, trifluoromethylbenzene and benzoic acid, give predominantly the corresponding meta fluoro-derivatives which is consistent with a typical electrophilic substitution process. Also, fluoro-, chloro- and bromo-benzenes are deactivated with respect to benzene itself but are fluorinated preferentially in the ortho and para positions [139]. At higher temperatures, polychlorobenzenes undergo substitution and addition of fluorine to give chlorofluorocyclohexanes [136]. 

Hence, in highly acidic media, fluorine may act as a very powerful and selective electrophile and, by this method, 2,4-difluorobenzoic acid, which is highly deactivated towards electrophilic attack, can be fluorinated in concentrated sulphuric acid to such an extent that 2,3,4,5-tetrafluoro- and even small amounts of pentafluoro-benzoic acid are produced [146,147]. 

The presence of a 9x-fluorine in a 11/l-hydroxy-A4-3-oxo steroid 10 results in completely stereospecific alkaline epoxidation with hydrogen peroxide to give 11 in a much slower reaction (4 d vs 4h) than that of the nonfluorinated analog.19 The nonfluorinated C = C bond in 3-perfluoroalkylated prop-1-ene 12 is epoxidized, with difficulty, in 7 days by 3-chloroperoxy-benzoic acid to give 13.20... 

With perfluorobenzoic acid, the attempted replacement of one fluorine by methanethiol in the ethylene glycol/pyridine system resulted in a 60% yield of a 4-methylsulfanyl-substituted product in which the carboxy group is replaced by hydrogen.38 However, in methanol (16 h reflux, with NaOMe). tetrafluoro-4-(mcthylsulfanyl)benzoic acid was obtained in 83% yield,43 and in refluxing propan-2-ol, tetrafluoro-4-(methylsulfanyl)benzenemethanol was obtained in 73% yield.44... 

The same study has shown that the organization completely changes for the corresponding benzoic acid 23 (Fig. 10) where the COOH groups form cyclic dimers with a linear shape.10 In this case there is no interdigitation of the Rp-chains and a (tilted) double layer structure is formed (see Fig. 11c), which is in line with the dll ratio of 1.6-1.7 observed for these benzoic acids. Related types of LC structures have been discussed for other partly fluorinated 4-alkoxybenzoic acids [126], and succinimidyl benzoates 24 [121]. 

Hence, benzoic acids can be more appropriately considered as self-assembled rod-like mesogens with two fluorinated terminal chains (see Sect. 4.4). 

Fig. 16 Representative examples of semiperfluorinated benzoic acids and methyl benzoates with fluorinated chains (77°C) [126, 133, 134, 136, 144-146]...

Fig. 20 Sequence of LC phases formed by hydrogen bonded complexes between substituted 1,3,5-triazines with complimentary benzoic acids depending on the number of chains and degree of fluorination (R1-R5 = ORF, ORjj, H) [153]...

Hydrogen bonded dimers of 4-RF-substituted benzoic acids [119, 120, 122, 126], /rcyclohexane carboxylic acids [120], and hydrogen bonded complexes of benzoic acids with 4,4 -bipyridine and stilbazole [166, 243-246] can be regarded as supramolecular rod-like mesogens with two fluorinated chains. Figures 33 and 34 show comparisons of selected benzoic acid dimers and their bipyridine and stilbazole complexes. Comparison of the benzoic acid dimers 122 and 123 with -alkyl chains and F-terminated -alkyl chains, respectively, indicates that a single F-atom at the end of the alkyl chain reduces the mesophase stability... 

Recently fluorinated chains were also attached to amine based dendrimers, like PPI and poly(amido amine) (PAMAM), by means of ionic self assembly with semiperfluorinated alkanoic acids (Fig. 71, 216, 217). All dendrimer complexes 216 with perfluorinated alkanoic acids show SmA phases except the fifth generation dendrimer which shows a Colrec phase [378]. Also semiperfluorinated 4-alkoxybenzoic acids 217 [379] and mixed systems combining fluorinated and nonfluorinated alkanoic or benzoic acids (216, 217) have been reported [379-381]. In most cases layer structures (SmA) and for higher generation dendrimers also modulated SmA phases (Colrec phases) were observed. The layer thickness of the SmA phases of the mixed complexes 216 depends on the ratio of fluorinated and non-fluorinated acids, where smaller d values were observed for dendrimers with low Rp-content for Rp-rich dendrimers the more rigid Rp-chains provide... 

In addition, taper-shaped and dendritic units were connected either covalently (at the apex or at the periphery) [133,135, 383,405] or by means of self assembly (e.g., hydrogen bonding [399]) to a polymer backbone. For example, polymers based on poly[4-(3-methacryloylpropyl]pyridine] form hydrogen bonded complexes with partially fluorinated mono-, di-, or trisubstituted benzoic acids (see complex 221 in Fig. 72). The type of mesophase formed by these complexes varies from smectic via columnar to cubic, most probably micellar cubic, with rising... 

New aspects of the chemistry of 2,4,6-tris(tri-fluoromethyl)benzoic acid and related compounds./. Fluorine Chem. 1991, 52, 99-105. 

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