The microanalysis of fluorine-containing organic compounds

Summary The method previously described for the micro-determination of fluorine in organic compounds by fusion with alkali metal in a nickel bomb followed by a thorium nitrate titration using a back-titration procedure, has been modified to meet the interferences caused by the presence of phosphorus and arsenic in the organic compound. The method ofOverman andGarrett for the removal of phosphate and arsenate ions by the addition of solid zinc carbonate was adapted for the quantitative removal of those ions. Difficulties in the determinations of carbon and hydrogen in fluoro-phosphorus compounds were overcome by mixing the samples with tungstic oxide.

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Zusammenfassung Die früher beschriebene Methode zur Mikrobestimmung von Fluor in organischen Verbindungen durch Schmelzen mit Alkalimetall in einer Nickelbombe und nachfolgende Titration mit Thoriumnitrat unter Verwendung eines Rücktitrationsverfahrens wurde weiter ausgearbeitet, um Störungen durch allenfalls anwesenden Phosphor oder Arsen zu vermeiden. Die vonOverman undGarrett angegebene Bindung von Phosphat und Arsenat durch Zusatz von festem Zinkcarbonat wurde zu einer quantitativen Entfernung dieser Ionen entwickelt. Schwierigkeiten bei der C-H-Bestimmung in fluor- und phosphorhältigen Verbindungen können durch Mischen der Probe mit Wolframoxyd umgangen werden.

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Résumé Les perturbations apportées par la présence du phosphore et de l'arsenic ont conduit à modifier la méthode antérieurement décrite pour le microdosage du fluor dans les composés organiques et qui comportait une fusion en présence d'un métal alcalin dans une bombe de nickel suivie par un titrage par le nitrate de thorium d'après une technique de dosage en retour. La méthode deOverman etGarrett pour l'élimination des ions phosphate et arseniate par addition de carbonate de zinc solide a été adaptée à l'élimination quantitative de ces ions. Les difficultés rencontrées lors du dosage du carbone et de l'hydrogène dans les composés simultanément fluorés et phosphorés ont été surmontées par le mélange des prises d'essais avec de l'oxyde tungstique.

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We wish to express our thanks to Dr.K. Sellars for the provision of samples and to Dr.J. C. Tatlow for his interest in this project.     

The microanalysis of fluorine-containing organic compounds

Summary Methods are described for the micro determination of chlorine, bromine, and iodine in organic compounds containing fluorine. The sample is heated with sodium in a nickel bomb, and the chloride ion produced is determined titrimetrically by a modified procedure involving the use of mercuric oxycyanide. Bromide is determined titrimetrically after oxidation to bromate with sodium hypochlorite; iodide is also determined by an amplified procedure after oxidation to iodate with bromine.The method has been extended to the simultaneous determination of chlorine, bromine, and iodine when present in organic compounds containing fluorine. All four halogens, and all possible combinations of halogens, can be determined in one compound after a single fusion.

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Zusammenfassung Es werden Methoden zur Mikrobestimmung von Chlor, Brom und Jod in fluorhaltigen organischen Substanzen beschrieben. Die Probe wird in einer Nickelbombe mit Natrium erhitzt. Das hierbei entstehende Chlorid wird mit Quecksilberoxycyanid nach einem modifizierten Verfahren titriert. Das Bromid wird nach Oxydation zu Bromat mit Natriumhypochlorit titriert. Das Jodid wird mit Brom zu Jodat oxydiert. Nach Zugabe von Jodid wird die sechsfache Jodmenge mit Thiosulfat bestimmt.Das Verfahren wurde für die gleichzeitige Bestimmung von Chlor, Brom und Jod in fluorhaltigen organischen Substanzen erweitert. Alle vier Halogene können somit unabhängig von ihrem gegenseitigen Verhältnis in einer Verbindung nebeneinander ineiner Einwaage bestimmt werden.

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Résumé Des méthodes sont décrites pour le microdosage du chlore, du brome, de l'iode dans les composés organiques contenant du fluor. L'échantillon est chauffé avec du sodium dans une bombe de nickel et l'ion chlorhydrique produit est déterminé titrimétriquement par une méthode modifiée mettant en jeu l'emploi d'oxycyanure mercurique. Le brome est dosé volumétriquement après oxydation en bromate a ec l'hypochlorite de sodium. L'iode est déterminé également par une methode amplifiée après oxydation en iodate par le brome.La méthode a été étendue au dosage simultané du chlore, du brome, de l'iode quand ils sont présents dans des composés organiques contenant du fluor. Les 4 halogènes et toutes les combinaisons possibles d'halogènes peuvent être déterminées sur un seul composé après une simple fusion.

     

The microanalysis of fluorine-containing organic compounds

Summary Kirsten's method for the determination of nitrogen has been applied to the analysis of fluorine-containing organic compounds. Some slight modifications to the original method have been introduced.

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Zusammenfassung Die vonKirsten angegebene Methode zur Bestimmung von Stickstoff wurde für die Analyse fluorhältiger organischer Verbindungen angewendet. Einige geringfügige Modifikationen des ursprünglichen Verfahrens werden angegeben.

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Résumé On a employé la méthode deKirsten pour la détermination de l'azote de composés organiques contenant du fluor. On a introduit quelques légères modifications à la méthode originale.

     

Computerized technique in organic microelemental analysis III. Automatic determination of fluorine in organic compounds

The automatic and computerized rapid microanalytical determination of fluorine in organic and organometallic compounds is an easily reproducible procedure. The procedure consists of the combustion of the compound in an empty tube; transfer of the combustion products to the titration vessel by automatic wash; and, finally, colorostatic titration of HF with Th(ClO₄), against alizarin red S.The entire analysis and preparation of the equipment for the next determination are programmed in the time of the 6-min cycle.The analyzer is interfaced to the departmental real-time time-sharing computer, along with electronic microbalances and other analyzers, as a part of the microanalytical laboratory computer service.Results of the analyses are reported on CR terminals and are also stored on the magnetic disk for further processing.     

Gas-chromatographic identification of fluorine-containing organic compounds

The gas-chromatographic retention of a series of fluoroalkylarenes on the standard nonpolar polydimethylsiloxane stationary phase OV-101 was characterized, and the retention indices of these compounds were determined. It was found that large negative values of the homological increments of these constants can serve as a sign of fluorine derivatives that contain no less than three fluorine atoms per molecule. The retention indices on polar inorganic sorbents, the silica gels Silipor 75 and Silipor 600, were chosen as the second chromatographic parameter. On these sorbents (unlike partition separation), the nonadditivity effect of the retention indices of polyfunctional organic compounds with respect to their simpler structural analogs was found for the first time. It was found that a mutual correlation between indices for this combination of a phase and a sorbent was lower than that for the combinations of phases with different polarities; this fact is responsible for the higher information content of this combination for the identification of compounds from this class.     

The semi-micro determination of fluorine,chlorine, and nitrogen in organic compounds

The organic compounds are fused with sodium in a nickel bomb in the usual way and the fluoride, chloride, and cyanide ions produced are determined. The method cannot be used to determine nitrogen in organic compounds containing oxygen since, in such cases, some of the nitrogen is converted to cyanate ion.     

Some aspects of plasma polymerization of fluorine-containing organic compounds. II. Comparison of ethylene and tetrafluoroethylene

Plasma polymerizations of ethylene and tetrafluoroethylene are compared. In the plasma polymerization of ethylene and of tetrafluoroethylene, glow characteristics play an important role. Glow characteristic is dependent on a combined factor of W/F_m, where W is discharge power and F_m is monomer flow rate. At higher flow rates, higher wattages are required to maintain “full glow.” In the plasma polymerization of tetrafluoroethylene, simultaneous decomposition of the monomer competes with plasma polymerization. Above a certain value of W/F_m, decomposition becomes the predominant reaction, and the polymer deposition rate decreases with increasing discharge power. ESCA results indicate that the plasma polymer of tetrafluoroethylene that is formed in an incomplete glow region (low W/F_m) is a hybrid of polymers of plasma polymerization and of plasma-induced polymerization of the monomer. Polymers formed under conditions of high W/F_m to produce “full glow” are similar, regardless of the extent of decomposition of the monomer. They contain carbons with different numbers of F(CF₃, ? CF₂? , >CF? , >C<) and carbons bonded to other more electronegative substituents.     

Studies on oxygen determination in organic microanalysis. II. On the microanalysis of oxygen by decrease in the quantity of anhydro-iodic acid

Summary Oxygen in organic compounds is determined by means of the decrease in weight of anhydro-iodic acid. Anhydro-iodic acid is stable in air and can be used for a long time. Satisfactory analyses are obtained.

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Zusammenfassung Sauerstoff kann in organischen Verbindungen durch Messung des Gewichtsverlustes der Anhydrojodsäure bestimmt werden. Diese ist an der Luft beständig und bleibt lange Zeit verwendungsfähig. Zufriedenstellende Analysenergebnisse werden erhalten.

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Résumé Le dosage de l'oxygène dans les composés organiques est effectué par la détermination de la diminution de poids de l'acide anhydroiodique. L'acide anhydroiodique est stable à l'air et peut être employé pendant des temps très longs. Des résultats satisfaisants ont été obtenus par les auteurs.

     

The micro-determination of carbon and hydrogen in fluorine-containing organic compounds

Summary The sample is burned in a silica combustion tube, using a 4 ml per minute oxygen stream. Oxidation of the combustion products is completed by passing them over a platinum contact heated to 750°C, after the manner ofFriedrich. Silver wool at the same temperature removes sulphur and halogens, including the fluorine from any hydrogen fluoride produced, and granular sodium fluoride at about 270°C is used to absorb silicon tetrafluoride.The water vapour and carbon dioxide are determined in the usual way by absorption in magnesium perchlorate and soda-asbestos respectively. Satisfactory results have been obtained for the analyses of 4 mg samples of compounds containing the elements C, H, O, F, the standard deviation of the results for hydrogen being about ±0,1% H and for carbon being about ±0,2% C.Preliminary work indicates that fluorocarbons may be analysed if water-vapour is introduced into the system, and that the presence of nitrogen in compounds presents no difficulty when an external absorbent for nitrogen oxides is used. Certain refinements are included, which are applicable to the conventional apparatus for micro carbon and hydrogen determination.

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Zusammenfassung Zur Bestimmung von Kohlenstoff und Wasserstoff in fluorhaltigen organischen Verbindungen wird die Substanz in einem Quarzverbrennungsrohr im Sauerstoffstrom von 4 ml/Minute verbrannt. Die vollständige Oxydation der Verbrennungsprodukte erfolgt nachFriedrich durch Überleiten über einen Platinkontakt bei 750°C. Bei derselben Temperatur hält Silberwolle Schwefel und alle Halogene einschließlich Fluor zurück, soweit es als Fluorwasserstoff vorliegt. Zur Absorption von Siliciumtetrafluorid wird gekörntes Natriumfluorid bei etwa 270°C verwendet.Wasserdampf und Kohlendioxyd werden in der üblichen Weise mittels Magnesiumperchlorat bzw. Natronasbest bestimmt. Bei Einwaagen von 4 mg Substanz irgendeiner Verbindung der Elemente C, H, O und F werden befriedigende Ergebnisse erhalten. Die durchschnittlichen Abweichungen von der Theorie betragen für Wasserstoff etwa ±0,1%, bei Kohlenstoff etwa ±0,2%.Vorversuche haben gezeigt, daß fluorhältige Kohlenwasserstoffe bei gleichzeitiger Zufuhr von Wasserdampf in die Apparatur analysiert werden können und daß die Gegenwart von Stickstoff in der Analysensubstanz keine Schwierigkeiten mit sich bringt, wenn ein zusätzliches Absorptionsmittel für Stickstoffoxyde vorgesehen ist. Einige Verbesserungen der herkömmlichen Apparatur für die Mikro-C-H-Bestimmung werden angeführt.

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Résumé L'échantillon est brûlé dans un tube à combustion en silice, utilisant un débit d'oxygène de 4 ml par minute. L'oxydation des produits de combustion se complète en les faisant passer sur un contact de platine chauffé à 750° C d'après le procédé deFriedrich. La laine d'argent à la même température élimine le soufre et les halogènes y compris le fluor de tout fluorure produit et le fluorure de sodium granulaire à 270° environ sert à absorber le tétrafluorure de silicium.La vapeur d'eau et le gaz carbonique sont dosés comme d'habitude par absorption sur le perchlorate de magnésium et l'amiante sodé respectivement. Des résultats satisfaisants ont été obtenus pour les analyses de 4 mg d'échantillons de composés contenant les éléments C, H, O, F; l'erreur moyenne des résultats pour l'hydrogène étant ±0,1% H et pour le carbone, environ ± 0,2% C.Un travail préliminaire indique que les hydrocarbures fluorés peuvent être analysés si l'on introduit de la vapeur d'eau dans le système et que la présence d'azote dans les composés ne présente pas de difficulté quand on utilise un absorbant extérieur pour les oxydes de l'azote. Certaines améliorations applicables à l'appareil classique pour les microdosages de carbone et d'hydrogène sont incluses.

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With 4 Figures.     

The geometry of intermolecular interactions in some crystalline fluorine-containing organic compounds

The propensity of C-F groups to form C-F H-C interactions with C-H groups on other molecules has been analyzed. Crystal structures of molecules containing only carbon, hydrogen, and fluorine, but no oxygen, nitrogen, or other hydrogen-bond-forming elements, were chosen for an initial study in which the intermolecular interactions in crystal-structure determinations of polycyclic aromatic hydrocarbons and their analogous fluoro derivatives were analyzed. It is found that C-F H-C interactions occur, but they are weak, as judged by the intermolecular distances and the angles involved. In a study of crystal structures of molecules containing other elements in addition to carbon, hydrogen, and fluorine, it was found that when an oxygen atom is in a neighboring position on an interacting molecule, a C-O group is more likely than a C-F group to form a linear interaction to the hydrogen atom of a C-H group. Thus, in spite of the high electronegativity of the fluorine atom, a C-F group competes unfavorably with a C-O^–, C-OH, or C=O group to form a hydrogen bond to an O-H, N-H, or C-H group. It is found, however, particularly for polycyclic aromatic hydrocarbons with substituted CF₃ groups that, in the absence of other functional groups that can form stronger interactions, C-F H-C interactions may serve to align molecules and give a different crystal packing from that in the pure hydrocarbon (where fluorine is replaced by hydrogen). Thus, C-F H-X (X = C, N, O) interactions are very weak, much weaker than C=O H-X interactions, but they cannot be ignored in predictions of modes of molecular packing in complexes and in crystals.     

Oxygen determination in organic fluorine compounds by means of a glassy-carbon pyrolysis tube

A conventional apparatus for determination of oxygen in organic compounds has been improved for application to organic fluorine compounds. A feature of the apparatus is the use of a pyrolysis tube made of glassy carbon instead of quartz, which eliminates effects due to hydrogen fluoride produced in pyrolysis of the sample. Ten analyses of dexamethasone with the apparatus gave a mean value of 20.44% for oxygen (theory, 20.38%), with a standard deviation of 0.16%. Oxygen in 9 organic fluorine compounds was accurately determined by using the apparatus, with an average error of +0.1%. One analysis by a gravimetric or a coulometric method took about 40 or 25 min, respectively.     

Some aspects of plasma polymerization of fluorine-containing organic compounds

The polymerization of perfluorocarbons and fluorohydrocarbons was investigated by using both continuous and pulsed rf discharge (100 μsec on and 900 μsec off). Plasma polymerization of perfluorocarbons is generally slower than that of hydrocarbons, which seems to be due to the absence of contribution of fluorine detachment to the plasma polymerization. Presence of multiple bond(s) or cyclic structure in a monomer is necessary to obtain high enough polymerization; however, the plasma polymerization mechanism postulated to plasma polymerization of hydrocarbons is still valid to these monomers. Cyclic structure is very effective to enhance the plasma polymerization capability of perfluorocarbons. Saturated straight-chain perfluorocarbons do not polymerize well in plasma, but the grafting of fluorine-containing functions on the surface of polymeric substrate can be achieved by the plasma of these compounds. The effect of pulse on the plasma polymerization was found to be similar to that found for hydrocarbons.     

Determination of fluorine in organic and organometallic compounds

Summary A method is described for the determination of fluorine in organic and organo-metallic compounds. Following oxygen-filled flask combustion in a silica flask, an aliquot of the absorbent solution is analysed for fluoride by a standard addition technique utilising a fluoride selective electrode.

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Fluorbestimmung in organischen und metallorganischen Verbindungen

Zusammenfassung Nach Verbrennung im sauerstoff-gefüllten Quarzkolben wird ein gemessener Teil der Absorptionslösung nach der Standard-Zusatztechnik mit Hilfe einer fluorspezifischen Elektrode analysiert.