[Determination of two perfluorinated compounds in urine by liquid chromatography-tandem mass spectrometry].

Objective: To establish a method for the determination of two perfluorinated compounds in urine by liquid chromatography-tandem mass spectrometry. Methods: In November 2022, urine samples were extracted by acidic methanol, purified by WAX solid phase extraction column, and eluted with methanol water, then Waters ACQUITY UPLC BEH C18 column (100 mm×2.1 mm, 1.7 µm) was used with 1.0 mmol/L ammonium acetate solution and methanol as mobile phase. The gradient elution was carried out, the detection was carried out by electrospray negative ion multiple response monitoring (MRM) mode, and the quantitative method was internal standard method. Results: Perfluorooctanoic acid and perfluorooctane sulfonic acid had a good linear relationship in the concentration range of 0.5-50.0 µg/L, and the correlation coefficient was >0.999. The limit of detection was 0.017 µg/L, and the limit of quantitation was 0.005 µg/L. The average recoveries were 96.3% and 101.8%, respectively. Days of precision were 3.5%-6.2% and 3.1%-7.4%, respectively, daytime precision were 4.3%-6.8% and 4.7%-8.1%, respectively. Conclusion: The established method of liquid chromatography-tandem mass spectrometry is high sensitivity and accuracy, and is suitable for the determination of perfluorooctanoic acid and perfluorooctane sulfonic acid in human urine.

Endemic dental fluorosis in children from a brazilian slave-descendent community: a cross-sectional study / Fluorose dentária endêmica em crianças de uma comunidade quilombola brasileira: um estudo transversal

Although fluoride (F) is required for the normal growth and development of several human organs and tissues, excessive exposure to it may be potentially toxic. Groundwater may present ranging levels of F; however, the appearance, taste, and smell are not altered. Thus, the present study aimed to evaluate dental fluorosis in children from a Brazilian slave-descendent community, as well as to assess F levels in the drinking water supplies available in that area. For that, 21 children aged from 6 to 14 years living in Rincão dos Martimianos were invited to participate. Thylstrup and Fejerskov index (a 0­9 scale) was used to assess dental fluorosis on permanent teeth. Furthermore, the F concentration of two water samples (from the artesian well and a tank) was determined by using a potentiometric method. All children presented dental fluorosis to some degree, ranging from score 2 to 9. About 81% of them had dental fluorosis scores equal to or over 5. Scores lower than 5 were observed only in children younger than 8 years; on the other hand, all children older than 8 years presented scores higher than 5. Moreover, artesian well water had an F concentration of 5 mg/L and tank water 0.8 mg/L. It is suggested that the F-rich groundwater supply was most probably responsible for dental fluorosis in that area. Brazilian slave-descendent communities, therefore, should receive constant attention from their local authorities in order to guarantee a proper water supply for consumption, as well as to provide public health education(AU)

Embora o flúor (F) seja necessário para o crescimento e desenvolvimento normal de vários órgãos e tecidos humanos, a exposição excessiva pode ser potencialmente tóxica. As águas subterrâneas podem apresentar níveis variados de F; no entanto, a aparência, o sabor e o cheiro não são alterados. Desta forma, o presente estudo teve como objetivo avaliar a fluorose dentária em crianças de uma comunidade brasileira descendente de escravos, bem como avaliar os níveis de F na água potável disponível nessa área. Para isso, 21 crianças de 6 a 14 anos residentes no Rincão dos Martimianos foram convidadas a participar da pesquisa. O índice de Thylstrup e Fejerskov (uma escala de 0 a 9) foi usado para avaliar a fluorose dentária em dentes permanentes. Além disso, a concentração de F de duas amostras de água (do poço artesiano e de um tanque) foi determinada pelo método potenciométrico. Todas as crianças apresentaram algum grau de fluorose dentária, variando de 2 a 9. Cerca de 81% delas apresentaram escores de fluorose dentária iguais ou superiores a 5. Escores inferiores a 5 foram observados apenas em crianças menores de 8 anos; por outro lado, todas as crianças maiores de 8 anos apresentaram escores superiores a 5. Além disso, a água do poço artesiano tinha concentração de F de 5 mg/L e a água do tanque 0,8 mg/L. Desta forma, acredita-se que a fonte de água subterrânea rica em F foi provavelmente responsável pela fluorose dentária na região avaliada. As comunidades quilombolas brasileiras, portanto, devem receber atenção constante de suas autoridades locais, a fim de garantir o abastecimento adequado de água para consumo, bem como proporcionar educação em saúde pública(AU)

Catalytic stereoselective Mannich-type reactions for construction of fluorinated compounds.

For its unique role in developing and designing new bioactive materials and healthcare products, fluoro-organic compounds have attracted remarkable interest. Along with ever-increasing demand for a wider availability of fluorine-containing structural units, a large diversity of methods has been introduced to incorporate fluorine atoms specially in a stereoselective fashion. Among them, catalytic Mannich reaction can proceed with a broad variety of reactants and open clear paths for the synthesis of versatile amine synthons in the synthesis of natural product and pharmaceutical molecules. This review provides an overview of the employment of catalytic asymmetric Mannich reactions in the synthesis of fluorine-containing amine compounds and highlights the conceivable distinct mechanisms.

[Analysis on results of occupational health examination in 677 workers exposed to inorganic fluorine].

Objective: To analyze the health hazards of fluorine and its inorganic compounds to workers exposed to fluorine, and to provide technical support for the protection of workers exposed to fluorine and the revision of occupational disease diagnostic standards. Methods: In January 2019, 677 workers exposed to fluorine in a fluorine chemical company in Hunan Province were selected by cluster sampling, and occupational health examination was conducted. The suspected occupational poisoning workers were diagnosed as occupational diseases, which were divided into poisoning group and non-poisoning group. T test and Pearson χ(2) test were used for statistical analysis. Results: A total of 73 occupational chronic fluorosis patients were diagnosed. 93.15% (68/73) of the skeletal lesions were multiple, and the most frequent sites were the upper tibia and fibula. 35.00% (21/60) , 50.00% (18/36) and 58.82% (10/17) of the tibia, fibula, ulna and radius had periosteal changes only on one side. Other abnormal results were mainly dental calculus (60.71%, 411/677) , fatty liver (48.89%, 331/677) , abnormal electrocardiogram (44.17%, 299/677) , decreased bone mass (33.53%, 227/677) and increased ALT (13.15%, 89/677) . Compared with non-poisoning group, the age, length of service exposed to fluoride and fatty liver detection rate of poisoning group were higher, and the differences were statistically significant (P<0.01) . Conclusion: The changes of long bone caused by inorganic fluoride only occur in one side, so the basic location of occupational health examination should include bilateral long bone to avoid missed diagnosis. It is difficult to diagnose occupational poisoning with single slight periosteal ossification, it is suggested that the standard should be revised to specify the degree.

Layered double hydroxides for controlled fluoride release

Abstract This study aims to develop a nano-sized fluoridated layered double hydroxide (LDH)-based release system via hydrothermal treatment for the controlled delivery of fluoride (F-) ions in the oral environment. The synthesis of conventional LDH-type (C-LDH) precursor nanomaterials was conducted using a co-precipitation method at constant pH, and the nanoparticulate-LDH (N-LDH) was synthesized by a hydrothermal procedure. Fluoride LDH (F-LDH) products were obtained through indirect synthesis using the precursor ion-exchange technique by varying the agitation time (2 and 24 h) and temperature (25 and 40 °C) to produce 12 material samples. The materials were characterized by energy dispersive x-ray, hexamethyldisilazane, digital radiography x-ray, Fourier-transform infrared, thermogravimetric analysis, and scanning electron microscopy. Additionally, the F-release kinetic profile was evaluated for 21 d in neutral and acid media with mathematical model analysis. Products with varying F-quantities were obtained, revealing specific release profiles. In general, there was a higher F-release in the acid medium, with emphasis on F-LDH-8. Fluoride-LDH and controlled fluoride delivery was successfully obtained, proving the potential of these nanomaterials as alternative anti-caries agents.

Study of Demineralized Dental Enamel Treated with Different Fluorinated Compounds by Raman Spectroscopy.

BACKGROUND: Current diagnostic methods for enamel caries detection are unable to detect caries lesions (incipient caries lesion) at a very early stage. OBJECTIVE: This study aims to determine the remineralizing effect of three fluorinated compounds on demineralized subsurface tooth enamel using Raman spectroscopy characterization. MATERIAL AND METHODS: In this experimental study, sixty impacted 3rd molars, with intact anatomical crowns recently extracted and without structural defects, were sectioned longitudinally in a mesio-distal direction using a diamond disc, obtaining two working surfaces (buccal and lingual). The 120 working surfaces obtained were immersed for 96 h in a demineralization solution at 37°C in order to demineralize the enamel surface. All samples were randomly divided into three groups (n=30 each) and their surfaces were treated with silver diamine fluoride (SDF), Difluoride silane (DSF), and acidulated phosphate fluoride (APF), and with no treatment undertaken in the control group (CG). The samples were immersed in alternating solutions for demineralization and remineralization at pH 4.4 and pH 7.0, respectively. The results were analyzed with Principal Component Analysis (PCA) in order to determine the variance. RESULTS: The most important difference (91.7%) is observed in APF group between PCA1 respect to PCA2, followed by DSF (91.5%) and SDF (76.3%) respectively. Therefore, a greater remineralization in the dental enamel can be observed by the three experimental groups. CONCLUSION: The APF and DSF have the effect of recovering the mineralization of dental enamel, except for the SDF. Functional groups OH- and PO43- were identified in all subsurface.

Prevention of dental caries by regular overnight application of a low-concentration fluoride gel loaded in a custom tray in patients undergoing radiotherapy for head and neck cancer: A preliminary study.

BACKGROUND: Some studies have reported topical application of 1.0%-2.0% fluoride gel in a custom tray for 4-5 minutes every day for the prevention of radiation-related dental caries. However, in Japan, the concentration of fluoride used by patients is limited to less than 0.15%. The efficacy of a low-concentration fluoride gel in a custom tray for the prevention of radiation-related dental caries has not been investigated. Methods and Material: In this preliminary study, we enrolled 13 patients with head and neck cancer who underwent radiotherapy. They wore a custom tray containing 0.145% sodium fluoride gel during sleep every night and were examined for newly developed dental caries 1 year later. Results: No new dental caries were found in the 13 patients 1 year after radiotherapy, and no adverse events were observed. CONCLUSIONS: We conclude that low-concentration fluoride gel in a custom tray during sleep could prevent radiation-related dental caries, and we plan to conduct a multi-center phase III randomized controlled trial to examine the efficacy of this method for the prevention of radiation-related dental caries.

Fluorine and Lithium: Ideal Partners for High-Performance Rechargeable Battery Electrolytes.

Further enhancement in the energy densities of rechargeable lithium batteries calls for novel cell chemistry with advanced electrode materials that are compatible with suitable electrolytes without compromising the overall performance and safety, especially when considering high-voltage applications. Significant advancements in cell chemistry based on traditional organic carbonate-based electrolytes may be successfully achieved by introducing fluorine into the salt, solvent/cosolvent, or functional additive structure. The combination of the benefits from different constituents enables optimization of the electrolyte and battery chemistry toward specific, targeted applications. This Review aims to highlight key research activities and technical developments of fluorine-based materials for aprotic non-aqueous solvent-based electrolytes and their components along with the related ongoing scientific challenges and limitations. Ionic liquid-based electrolytes containing fluorine will not be considered in this Review.

Determination of Fluorine Chemical Structure in Slag by Thermal Hydrolysis He-MIP-OES.

A novel microwave-induced helium plasma optical emission spectrometry (He-MIP-OES) combined with a thermal hydrolysis sample introduction system was newly established for the determination of fluorine (F) compounds in slags. The MIP maintained through an Okamoto cavity was adopted, which was quite stable and provided a higher detection capability of F by helium plasma. The basic analytical performance of He-MIP-OES combined with an ultrasonic nebulizer for F analysis was also examined, and expected results could be obtained. The thermal hydrolysis behavior of CaF2, Ca4(Si2O7)(F,OH)2 and Ca5(PO4)3F, as known F chemical structures in slag, was also examined by thermal hydrolysis He-MIP-OES; F compounds in actual slag could be successfully identified and determined by this developed system.

Analysis of fluoride concentration in commercial bottled waters / Análise da concentração de flúor em águas comercializadas

Objective: Evaluate fluoride concentration in 500ml commercial brands of bottled water and compare it to the amount ​​printed on the label. Methods: A descriptive, cross-sectional epidemiological study was conducted. Samples of nine different commercial brands of 500ml bottled water were collected at authorized distribution points in the city of Fortaleza, CE, Brazil, in 2013. Fluoride concentration was determined in duplicate using a fluoride ion-selective electrode. The results were obtained from linear regression of the calibration curve. Results: Fluoride concentrations ranged between 0.07 and 0.63 ppm F- or mg F/L. There were significant differences between the values ​​​​printed on the labels and those found in the analysis. The fluoride concentration levels determined were not in compliance with the recommended levels by the National Health Surveillance Agency. Conclusions: The results obtained confirm the need for more careful monitoring of fluoride levels in bottled water and closer sanitary inspections.

Objetivo: Avaliar a concentração de flúor na água engarrafada comercializada, com padrão de apresentação de 500 ml, comparando-a aos valores impressos no rótulo da embalagem. Métodos: Estudo epidemiológico, descritivo e transversal. Foram coletadas amostras das nove marcas disponíveis, na forma de apresentação de 500 ml, nos pontos de distribuição autorizados do município de Fortaleza, em 2013. A concentração de flúor foi determinada por análise em duplicata, utilizando o eletrodo íon-específico para fluoretos. Os resultados de concentração de flúor foram obtidos através da regressão linear da curva de calibração. Resultados: A concentração de flúor variou entre 0,07 e 0,63 ppm de flúor por mg/l, com diferenças significantes entre os valores estipulados nos rótulos e os encontrados com a análise, além de apresentar a concentração foram do padrão preconizado pela vigilância sanitária. Conclusões: Os resultados reforçam a necessidade de um controle dos níveis de flúor em águas engarrafadas, além de uma maior fiscalização por parte da vigilância sanitária.

Deposição óssea por fluoreto de alumínio: intoxicação ocupacional? / Bone deposition of aluminum fluoride: occupational poisoning?

Contexto: Paciente de 38 anos foi encaminhado por ordem judicial para ambulatório de saúde ocupacional de hospital público terciário com queixa de dor difusa em membros inferiores, superiores, coluna e bacia, além de dificuldade na deambulação. Trazia imagens de ressonância magnética e tomografia com sinais de osteosclerose/osteonecrose em diferentes ossos (tíbia, fêmur, úmero, osso da bacia). Havia sido atendido pela equipe de clínica médica do mesmo hospital e realizado biópsia de crista ilíaca, que evidenciou infarto ósseo e grande quantidade de alumínio ósseo. Tem histórico laboral de atividade na produção de alumínio durante quatro anos, em mineradora do estado do Maranhão. Objetivos: O presente trabalho tem como objetivo revisão na literatura de possíveis causas ocupacionais em distúrbios ósseos, e identificar elementos técnico-científicos que permitam relacionar a deposição óssea de alumínio com as alterações clínico-radiológicas do caso em questão. Métodos: Foi realizada revisão de literatura baseada em publicações nas principais bases de pesquisa (PubMed, SciELO, Lilacs), além de avaliação de etapas de beneficiamento do alumínio na indústria mineradora. Resultados: Por meio da constatação da exposição do trabalhador a subprodutos químicos do beneficiamento do alumínio metálico, que, sabidamente podem causar fluorose óssea, e a associação desta doença com os achados de exame radiológico, bem como sintomatologia apresentada por este trabalhador, é possível estabelecer nexo ocupacional. Conclusão: A sintomatologia apresentada pelo trabalhador, bem como suas alterações de exame de imagem e anatomopatológico, permitem inferência de causalidade entre a exposição a compostos de fluoreto e criólita e seu distúrbio ósseo.

Context: A 38 year old patient was referred by court order for occupational health medical service of tertiary public hospital complaining of diffuse pain in lower and upper limbs, spine and pelvis, and walking difficulty. Magnetic resonance imaging and tomography signs of osteosclerosis/osteonecrosis in different bones (tibia, femur, humerus, hip bone). He was seen by the medical clinic of the same hospital and some procedures have been performed, such as iliac crest biopsy, which revealed bone infarction and a large amount of aluminum bone. This patient has worked for four years in aluminum production, in Maranhão, Brazil. Objectives: This paper aims to review the literature of possible occupational causes for bone disorders and identify technical and scientific elements that may allow to relate the bone aluminum deposition with clinical and radiological changes of the case. Methods: For this purpose, we performed a literature review based on publications in major research bases (PubMed, SciELO, Lilacs), and evaluation stages of processing of aluminum in the mining industry. Results: Through the observation of the worker exposure to chemical byproducts from the processing of aluminum metal, which is known to cause skeletal fluorosis, and the association of this disease with radiological findings and symptoms presented by this paper, it is possible establish relationship between his occupational activity and the diasease. Conclusion: The symptoms presented by the worker, as well as their changes of imaging and pathologic examination, allow inference of causality between exposure to fluoride and cryolite compounds and their bone disorder.

Highly enantioselective copper(I)-catalyzed conjugate addition of terminal alkynes to 1,1-difluoro-1-(phenylsulfonyl)-3-en-2-ones: new ester/amide surrogates in asymmetric catalysis.

A highly enantioselective copper-catalyzed conjugate alkynylation of monoactivated enones, namely 1,1-difluoro-1-(phenylsulfonyl)-3-en-2-ones, is described. The reaction products are obtained with good yields and excellent enantioselectivities (from 92 to 99% ee). The ß-alkynylated difluoro(phenylsulfonyl) ketones can be converted into the corresponding ß-alkynylated difluoro- and trifluoromethyl ketones, esters and amides. This is the first example on the use of 1,1-difluoro-1-(phenylsulfonyl)-3-en-2-ones as substrates in an enantioselective reaction, which have been shown to be new ester/amide surrogates.

Synthesis of enones, pyrazolines and pyrrolines with gem-difluoroalkyl side chains.

Starting from easily accessible gem-difluoropropargylic derivatives, a DBU-mediated isomerisation affords enones in fair yields with a gem-difluoroalkyl chain. These derivatives were used to prepare pyrazolines and pyrrolines with the desired gem-difluoroalkyl side chain by cyclocondensations in good yields and with excellent stereoselectivity. A one-pot process was also successfully developed for these sequential reactions. By carrying out various types of Pd-catalyzed coupling reactions for compounds with a p-bromophenyl substituent a route to focused chemical libraries was demonstrated.

Efeito da aplicação tópica de um verniz de TiF4 quimicamente estável na desmineralização do esmalte dentário bovino: estudo in vitro / Effect of topical application of a chemically stable TiF4 varnish on the demineralization of bovine enamel: an in vitro study

Objetivo: Avaliar, in vitro, o efeito preventivo da aplicação tópica de um verniz à base de tetrafluoreto de titânio quimicamente estável e de um verniz à base de fluoreto de sódio sobre o esmalte bovino, mediante ciclagem de pH. Metodologia: A amostra foi constituída por 75 blocos de esmalte bovino 3×3 mm, sendo 15 aleatoriamente alocados em cada um dos cinco grupos: G1: Dentifrício Fluoretado + Verniz sem princípio ativo; G2: Dentifrício Fluoretado + Verniz à base de TiF4 (4 minutos); G3: Dentifrício Fluoretado + Verniz à base de TiF4 (24 horas); G4: Dentifrício Fluoretado + Verniz à base de NaF (24 horas); G5: Dentifrício Fluoretado. A ciclagem de pH foi realizada por um período de 14 dias, constando de oito ciclos, a 37 °C. Os blocos tratados foram mantidos em solução desmineralizante por oito horas e, por 16 horas, em solução remineralizante, sendo submetidos à análise da superfície em microscopia eletrônica de varredura e espectroscopia de energia dispersiva. Resultado: O verniz à base de TiF4 promoveu uma maior proteção ao esmalte quando comparado com os demais grupos. Mesmo após o período de ciclagem, foram encontrados fósforo, cálcio, sódio, magnésio, titânio, cloro, silício, alumínio, enxofre, potássio, oxigênio e flúor na superfície do esmalte. Conclusão: O aspecto da estrutura adamantina submetida à ação do tetrafluoreto de titânio revelou a presença de uma película protetora. O cálcio e o fósforo foram os principais compostos inorgânicos encontrados no esmalte, sendo observadas alterações na constituição química da camada superficial adamantina em função do tratamento com fluoreto instituído.

Objective: To evaluate the in vitro preventive effect of topical application of achemically stable titanium-tetrafluoride (TiF4) varnish and a sodium fluoride (NaF) varnish on bovine enamel by pH cycling test. Methodology: The sample consisted of 75 blocks of bovine enamel measuring 3x3mm, which were randomly assigned to 5 groups of 15, as follows: G1: Fluoridated dentifrice + varnish without active principle; G2: fluoridated dentifrice + TiF4 varnish (4 minutes); G3: fluoridated dentifrice + TiF4 varnish (24 hours); G4:fluoridated dentifrice + NaF varnish (24 hours); G5: fluoridated dentifrice.A pH cycling was carried out for a period of 14 days, consisting of 8 cycles at 37 °C. The treated blocks were kept in demineralizing and remineralizing solutions for 8 and 16 hours, respectively, being then subjected to surface analysis under scanning electron microscopy and dispersive energy spectroscopy. Result: The TiF4 varnishshowed a greater protection to enamel when compared with the other groups.Even after the cycling period, the following elements were found on the enamel surface: phosphorus, calcium, sodium, magnesium, titanium, chlorine, silicon, aluminum, sulfur, potassium, oxygen and fluorine. Conclusion: The adamantine structure subjected to the action of titanium tetrafluoride revealed the presence of a protective pellicle.Calcium and phosphorus were the major inorganic compounds found in enamel. Furthermore, there were changes in the chemical composition of the adamantine surface layer as a result of the treatment with fluoride.

Ionic Fluorination of Carbon Monoxide as a Route to Gasphase Carbonylation of Inert CH and NH Bonds.

Gaseous FCO+ ions from the ionization of mixtures of nitrogen trifluoride and carbon monoxide execute selective and efficient CO-functionalization of the C-H bonds of benzene and toluene and of the N-H bond of ammonia. The occurrence of these carbonylation reactions has been unambiguously ascertained by Fourier-transform ion cyclotron resonance (FT-ICR) spectrometry, and the details of the structure and the mechanism of formation of the precursor FCO+ ions have been investigated. FT-ICR experiments show that these ions, structurally assigned as F-C-O+ by collisionally activated dissociation (CAD) spectrometry, arise from the reaction of CO.+ with NF3 and of NF+2 with CO. Combining the latter F+ transfer with the independently observed fluoride-ion abstraction by FCO+ from NF3 results in a catalytic cycle in which gaseous NF+2 ions promote the conversion of carbon monoxide into carbonic difluoride, F2 CO, with nitrogen trifluoride as the source of F.

Determination of the Enthalpies of Combustion and Formation of Substituted Triazines in an Adiabatic Rotating Bomb Calorimeter.

To obtain reliable thermodynamic data on substituted triazines, it is necessary to use a calorimeter that is capable of high precision with small quantities of sample and in which a homogeneous solution of the corrosive combustion products can be maintained. The enthalpies of combustion of six substituted triazines have been determined in a platinum-lined adiabatic rotating bomb calorimeter. These are the first determinations of enthalpies of combustion or formation to have been reported for these compounds. The values derived for the enthalpies of formation in kJ/mol at 25 °C are as Follows: 2,4,6-trimethoxy-l,3,5-triazine, - 478.60± 0.87; 2,4,6-triethozy- 1,3,5-triazine, - 584.99± 1.50; 2,4,6-tris(2-fluoro-2,2-dinitroethoxy)-l,3,5-triazine, -1109.80±l.53; 2,4-dimethoxy-6-(2-fluoro-2,2-dimtroethoxy)-l,3,5-triazine, -697.08± 1,15; 2-methoxy- 4,6-bis(2-fluoro-2,2-dinitroethoxy)-l,3,5-triazine, -907.71± 2.40; 2-amino-4,6-bis(2-fluoro-2,2-dinitroethoxy)-l,3,5-triazine, - 773-12±1.50.

Fluorine Flame Calorimetry III. The Heat of Formation of Chlorine Trifluoride at 298.15 K.

The standard heat of formation of chlorine trifluoride (gas) at 298.15 K has been determined to be - 164.65 kj mol-1 (-39.35 kcal mol-1) with an overall experimental uncertainty of 5.14 kj mol-1 (1.23 kcal mol-1). This value is derived from the enthalpies of the following reactions which were measured directly in a flame calorimeter operated at 1 atm pressure and 303.5 K, together with data from previous investigations. ClF 3 ( g ) + 2 H 2 ( g ) + 100 H 2 O ( 1 ) → [ HC 1 ⋅ 3 HF ⋅ 100 H 2 O ] ( 1 ) ( 1 / 2 ) Cl 2 ( g ) + 1 / 2 H 2 ( g ) + [ 3 HF ⋅ 100 H 2 O ] ( 1 ) → [ HC 1 ⋅ 3 HF ⋅ 100 H 2 O ] ( 1 ) The enthalpy of formation of [HC1‧100H2O](l) was also measured. The average Cl - F bond energy in chlorine trifluoride is calculated to be 160.1 kj mol-1 (38.26 kcal mol-1).