Ion cyclotron resonance mass spectrometric study of ion—molecule reactions in toluene—pyridine mixtures

Ion—molecule reactions in toluene, toluene-d₈, pyridine, 4-methyl-, 4-ethyl- and 4-terr-butylpyridine and quinoline and their mixtures were studied by ICR mass spectrometry at 10^-7 Torr (1 Torr = 133.3 Pa). The reactions of benzyl (m/z 91), benzyl-d₇ (m/z 98), methylbenzyl (m/z 105), and azabenzyl (m/z 92) ions with pyridines and quinoline were observed. The reactions of protonated pyridines with unprotonated molecules leading to homoconjugated ions (BHB)⁺ were detected.     

Charge Localization: Doubly-Charged Ion Reactions in Toluene

The kinetic energy released in the major charge-separation reactions of [C₇H₈]⁺⁺ [C₇H₇]⁺⁺ and [C₇H₆]⁺⁺ formed from toluene, and in the corresponding reactions of toluene-α-d₃, toluene-d₈ and 2,3,4,5,6-toluene-d₆ has been measured. Some fragmenting [C₇]⁺⁺ ions are linear; in certain cases they have cyclic structures while in others ‘coiling’ of a linear ion to allow hydrogen transfer in the transition state is suggested. From relative metastable ion abundance data it is apparent that nearly complete H/D randomization accompanies these slow reactions.     

Utility of [4-(3-methoxyphenyl)pyrimidin-2-yl]cyanamide in synthesis of some heterocyclic compounds

N-[4-(3-Methoxyphenyl)pyrimidin-2-yl]cyanamide ( 1 ) was reacted with morpholine and respective binuclephilic reagents namely: ethylenediamine, o-phenylenediamine, o-aminothiophenol, or o-aminophenol to give the corresponding carboximidamide 2 , imidazolidine 3 , and benzazoles 4–6 . While its reaction with hydrazides in DMF at 90°C, gave the corresponding 1,2,4-triazols 7–11 . Also, treatment of cyanamide 1 with heterocycles having both nucleophilic and electrophilic groups (─NH₂/─COOEt) in iso-propanol in presence of catalytic amount of Conc. HCl, gave the corresponding thieno[2,3-d]pyrimidinone 12 and unexpected thieno[3,2-d]pyrimidine 13 instead of bis-thieno[3,2-d]pyrimidine 14 , respectively. While, its reaction with ethyl 5-amino-1,3-thiazole-4-carboxylate yielded the unexpected N-(pyrimidin-2-yl)urea 15 rather than the corresponding thiazolo[5,4-d]pyrimidine 16 . Unexpected N-(pyrimidin-2-yl)thiourea 17 was obtained, when cyanamide 1 reacted with potassium thiolates in iso-propanol with catalytic amount of Conc. HCl.     

Kinetics of the reactions of acenaphthene and acenaphthylene and structurally-related aromatic compounds with OH and NO3 radicals,N2O5 and O3 at 296 ± 2 K

The kinetics of the atmospherically important gas-phase reactions of acenaphthene and acenaphthylene with OH and NO₃ radicals, O₃ and N₂O₅ have been investigated at 296 ± 2 K. In addition, rate constants have been determined for the reactions of OH and NO₃ radicals with tetralin and styrene, and for the reactions of NO₃ radicals and/or N₂O₅ with naphthalene, 1- and 2-methylnaphthalene, 2,3-dimethylnaphthalene, toluene, toluene-α,α,α-d₃ and toluene-d₈. The rate constants obtained (in cm³ molecule^?1 s^?1 units) at 296 ± 2 K were: for the reactions of O₃; acenaphthene, <5 × 10^?19 and acenaphthylene, ca. 5.5 × 10^?16; for the OH radical reactions (determined using a relative rate method); acenaphthene, (1.03 ± 0.13) × 10^?10; acenaphthylene, (1.10 ± 0.11) × 10^?10; tetralin, (3.43 ± 0.06) × 10^?11 and styrene, (5.87 ± 0.15) × 10^?11; for the reactions of NO₃ (also determined using a relative rate method); acenaphthene, (4.6 ± 2.6) × 10^?13; acenaphthylene, (5.4 ± 0.8) × 10^?12; tetralin, (8.6 ± 1.3) × 10^?15; styrene, (1.51 ± 0.20) × 10^?13; toluene, (7.8 ± 1.5) × 10^?17; toluene-α,α,α-d₃, (3.8 ± 0.9) × 10^?17 and toluene-d₈, (3.4 ± 1.9) × 10^?17. The aromatic compounds which were observed to react with N₂O₅ and the rate constants derived were (in cm³ molecule^?1 s^?1 units): acenaphthene, 5.5 × 10^?17; naphthalene, 1.1 × 10^?17; 1-methylnaphthalene, 2.3 × 10^?17; 2-methylnaphthalene, 3.6 × 10^?17 and 2,3-dimethylnaphthalene, 5.3 × 10^?17. These data for naphthylene and the alkylnaphthalenes are in good agreement with our previous absolute and relative N₂O₅ reaction rate constants, and show that the NO₃ radical reactions with aromatic compounds proceed by overall H-atom abstraction from substituent-XH bonds (where X = C or O), or by NO₃ radical addition to unsaturated substituent groups while the N₂O₅ reactions only occur for aromatic compounds containing two or more fused six-membered aromatic rings.     

Order parameter studies from effective order geometry in 4O.Om and 7O.Om liquid crystalline compounds

The effective geometry parameter, α_g = n _o /n _e, is used to evaluate the orientational order parameter, S, in the case of N-(p-n-butyloxybenzylidene)-p-n-alkoxy anilines, 4O.Om and N-(p-n-heptyloxybenzylidene)-p-n-alkoxy anilines, 7O.Om compounds with m?=?3–7 and 9 in the former case and m?=?3, 5–7 and 9 in the later materials. The results obtained are compared with those calculated using the standard techniques of molecular polarisability and birefringence. The effective geometry parameter's influence on the deflection of light by the liquid crystal compounds is also studied. The variation of temperature gradient of the ordinary refractive index, dn _o /dT, and extraordinary refractive index, dn _e /dT, of the liquid crystals is also studied.     

Mechanism of the thermal decomposition of (η5-C5H5)Fe(CO)2(η1-acenaphthenyl)

The complexes (η⁵-C₅H₅)Fe(CO)₂(η¹-acenaphthenyl) (I), (η⁵-C₅H₅)Fe(CO)₂ (η¹-trans-β-deuterioacenaphthenyl) (II), and (η-C₅D₅)Fe(CO)₂, (η¹-acenaphthenyl) (XIII) have been prepared and their thermal decomposition studied in vacuo and in refluxing toluene. All three complexes decompose to produce mixtures of acenaphthene (VII), acenaphthylene (VIII), and [C₅H₅Fe(CO)₂]₂ (VI). Biacenaphthenyl (IX) is also obtained from the thermolysis of I in toluene. The formation of alkene VIII, and, to a lesser extent, alkane VII is suppressed by external CO. Thermolysis of I in toluene-d₈ and of II in vacuo and in toluene produces deuterium-enriched VII. The acenaphthene generated from the decomposition of XIII also contains deuterium. The above observations are accomodated by a mechanistic scheme involving competing β-elimination, ironcarbon bond homolysis to produce the acenaphthenyl radical, and CpH abstraction by an undetermined pathway.     

Effect of alcohol-water exchange and surface scanning on nanobubbles and the attraction between hydrophobic surfaces

4-(4′-Butoxyphenyl)phenyl-β-O-d-glucoside was synthesized as a low-molecular-mass gelator. It was able to immobilize a variety of aqueous and organic solvents in large amounts through the formation of three-dimensional self-assembled fibrillar networks. The morphologies of the aggregates depended on the nature of solvent where they were formed. Planar ribbons were observed in water, while helical ribbons were dominant in toluene and sheets in CHCl₃. The xerogel from water exhibited a lamellar structure with a d-spacing of 2.45 nm as demonstrated by 1D-WAXD, indicating a bilayer structure interdigitated with butoxy tails, whereas the xerogel from CHCl₃ or toluene yielded a lamellar structure with a d-spacing of 3.05 nm, implying a bilayer structure interdigitated with glycosyl heads. Increasing the content of 1,4-dioxane in water caused a gradual transformation from planar to twisted ribbons and then tubes.     

C–H bond activation versus ring cleavage in the gas phase ion-molecule reactions of Nb+ and Ta+ with toluene and picoline

The reactions of Nb⁺ and Ta⁺ with toluene and picoline and their deuterium-labelled analogues were studied in a Fourier transform ion cyclotron resonance mass spectrometer. Methyl substitution completely changes the reactivities relative to benzene and pyridine. Both metals react to dehydrogenate toluene exclusively. In contrast to benzene, no ring cleavage is observed in the Ta⁺/toluene reaction. A simple explanation for this difference in reactivities is proposed based on the relative energies of the Hückel orbitals of benzene and toluene. The (b₁) symmetric antibonding orbital is higher in energy for toluene. Population of this orbital is necessary for formation of the metallanorbornadiene intermediate and does not occur at thermal energies. Reaction with ring labelled toluene-d₅ shows exclusive H₂ or D₂ elimination in reaction with Nb⁺ and H₂, HD, and D₂ elimination in reaction with Ta⁺. Reactions with the picolines show both dehydrogenation and ring cleavage. Isotope labelling studies show facile H/D scrambling occurs in the intermediate ion-molecule complexes with HCN and DCN both eliminated from the methyl-d₃-2-picoline and 4-picoline. The metals react with picoline and pyridine by different mechanisms. The isotope labelling results suggest a metal-hydrido-azepinium structure for the intermediate complex.     

Heterocycles from Pyrazoloylhydroximoyl Chloride: Synthesis of Certain Quinoxaline,Benzothiadiazine, Benzoxadiazine,Quinazolinone, Imidazo[1,2-a]pyridine,Imidazo[1,2-a]pyrimidine,Isoxazole, Pyrazolo[3,4-d]pyridazine and Pyrrolidino[3,4-d]isoxazolin-4,6-dione Derivatives

3-Ethoxycarbonyl-5-methyl-1-(4-methylphenyl)-4-pyrazoloylhydroximoyl chloride (1) reacted with o-phenylenediamine, o-aminothiophenol, o-aminophenol and methyl anthranilate to afford 3-nitrosoquinoxaline, benzothiadiazine, benzoxadiazine, and 3-hydroxyquinazoline, respectively. Imidazo[1,2-a]pyridine, imidazo[1,2-a]pyrimidine and isoxazole derivatives were obtained via the reaction of 1 with 2-aminopyridine, 2-aminopyrimidine and the appropriate active methylene compounds, respectively. Pyrazolo[3,4-d]pyridazines, and pyrrolidino[3,4-d]isoxazolines derivatives were also synthesized. The structures of the newly synthesized compounds were established on the basis of spectral data and alternate synthesis whenever possible.     

The two-photon spectrum of toluene vapor

The two-photon excitation spectrum of toluene-h₈ and toluene-d₈ vapor has been recorded under low resolution (1 cm^?1) in the region of the S₁ ← S₀ (¹B₂ ← ¹A₁) transition. Although the electronic transition is formally allowed in two-photon spectroscopy, a large fraction of intensity exists in a subsystem induced by the out-of-phase CC stretching vibration ν₁₄ (b₂). Band contours associated with each of the two assigned tensor components of the transition are identified and partially analyzed by comparison with the two-photon contours of fluorobenzene.     

A new route to the synthesis of 4-amino-substituted pyrido[2,3-d]pyrimidin-5-one derivatives

The reaction of 6-(R-amino)-5-acetyl-4-methylsulfonyl-2-phenylpyrimidines with amines was studied. 6-Arylamino derivatives react with alkylamines to form 6-alkylamino-4-arylamino-5-acetyl-2-phenylpyrimidines, which upon refluxing in benzene with dimethylformamide dimethylacetal are converted to 4-alkylamino-8-aryl-2-phenylpyrido[2,3-d]pyrimidin-5(8H)-ones. The cyclization proceeds selectively with participation of the arylamino group only, the alkylamino group being not involved. At the same time, refluxing of 5-acetyl-4,6-dibenzylamino-2-phenylpyrimidine with dimethylformamide dimethylacetal in toluene affords the product of condensation on the acetyl group, which upon refluxing in o-xylene transforms to 4-benzylamino-8-benzyl-2-phenylpyrido[2,3-d]pyrimidin-5(8H)-one.

     

A low frequency assignment for infrared and Raman spectra of (+) bornyl acetate using related compounds and deuterated derivatives

Twenty-one fundamentals of (+)-bornyl acetate and nine deuterium substituted modifications (2-d₁; 3,3-d₂; 2,3,3-d₃; acetate-d₃; 2-d₁ acetate-d₃; 3,3-d₂ acetate-d₃; 2,3,3-d₃ acetate-d₃; 10-d₁; 10,10,10-d₃) as well as (−)-isobornyl-1-10,10.10-d₃ acetate have been assigned between 200 and 850cm⁻¹. These results supplement the previous assignment of nineteen fundamentals of (−)-isobornyl acetate and seven deuterium substituted modifications (2-d₁,; 3,3-d₂; 2,3,3-d₃; acetate-d₃; 2-d₁ acetate-d₃; 3,3-d₂ acetate-d₃; 2,3,3-d₃ acetate-d₃) between 200 and 900cm⁻¹ [8]. These fundamentals are: skeletal vibrations of the quaternary carbons, ring breathing, bending, and twisting vibrations, and vibrations of the acetate group. Key model compounds used in this analysis are norbornane, neopentane, methyl acetate, cyclopentanol, and the (−)-isobornyl acetate system. A series of related compounds (norbornane, bornane, endo-norbomyl acetate, 1-methyl-endo-norbornyl acetate, apobornyl acetate, and (+)-bornyl acetate) is used to identify frequencies associated with the quaternary carbon and the acetate group. Raman spectra are more useful for the quaternary carbon frequencies and i.r. spectra are more useful for acetate group frequencies. Four exo stereoisomer alcohols (1-methyl-exo-norborneol, 1-methy d₃-exonorborneoI, apoisoborneol, (−)-isoborneol) and three endo stereoisomer alcohols (1-methyl-endo-norborneol, apoborneol, (+)-borneol) serve as model compounds for a modification of the earlier assignment [8] for the skeletal stretching of the quaternary carbons in the (−)-isobornyl acetate system and extension of this modified assignment to the (+)-bornyl acetate system. Quaternary carbon symmetric skeletal stretching is believed to be responsible for prominent Raman bands between 580 and 680cm⁻¹ in the 36 bicyclic ring compounds investigated to date. Fermi resonance is proposed as the explanation for a number of unexpected intensity patterns observed in the i.r. and Raman spectra.     

Polymerization of [o-(trimethylgermyl)phenyl] acetylene and polymer characterization

[o-(Trimethylgermyl)phenyl]acetylene was polymerized in the presence of WCl₆, W(CO)₆-hv, etc., to give polymers whose weight-average molecular weights reached ca. 7.0 X 10⁵ at the highest. When the MoOCl₄-n-Bu₄Sn-EtOH (1 : 1 : 1) catalyst was used, the polydispersity ratio of the polymer obtained was 1.08, and the number-average molecular weight increased in direct proportion to monomer conversion; these indicate that this polymerization is a living polymerization. The polymer had the structure ? [CH?C(C₆H₄-o-GeMe₃)]_n ? and was a dark purple solid (λ_max = 551 nm, ε_max = 6100 M^-1 cm^-1 in THF) soluble in organic solvents such as toluene and chloroform. The onset temperature of weight loss of the polymer in TGA in air was ca. 230°C, and the glass transition temperature was above 180°C. The Po₂ of the present polymer is 105 barrers—larger than the value of natural rubber and fairly close to that of poly(dimethylsiloxane). © 1993 John Wiley & Sons, Inc.     

Cascade C?N and C?O bond constructions for the synthesis of dibenzoimidazo[1,4]oxazepines catalyzed by CuI/o-phen

A novel method for the synthesis of dibenzo[b,f]imidazo[1,2-d][1,4]oxazepine derivatives was described via cascade Csp² N and Csp² O bond constructions. It was a crossed double Ullmann reactions using 4,5-diaryl-2-(2-hydroxylphenyl)-1H-imidazole as the double nucleophilic centers in the presence of Cs₂CO₃, while 1-bromo-2-iodobenzene was used as a substrate catalyzed by CuI and o-phenanthroline in good yields.     

The versatile chemistry of thiophenes: The effects of b-side contra c-side annelation on reactivity

The synthesis of the nine dithienopyridines and twenty-four thienonaphthyridines with angular annelation is described. They are all conveniently obtained by Pd(0)-catalysed couplings between heterocyclic o-formylboronic acids or o-formylstannyl derivatives with heterocyclic o-amino-halo derivatives. The effect of the use of silver oxide and cupric oxide as co-reagent is discussed. Differences in electrophilic substitution, metalation and cycloaddition of b- and c-fused isomers is treated. Theoretical calculations at the RHF/3–21G* level are in agreement with the orientation and reactivity in the nitration of dithieno[3,4-b:3′,4′-d] pyridine and dithieno[2,3-b:3′,2′-d] pyridine observed experimentally. The preparation of N-oxides of the above-mentioned ring-systems and their reactivity will also be discussed.     

Synthetic utility of a heterocyclic o-aminoaldehyde: synthesis of pyrazolopyridopyrimidines, pyrazolonaphthyridines, and pyrazolopyrimidonaphthyridinones

Abstract  

A series of various polysubstituted pyrazolo[3,4-h][1,6]naphthyridines, benzo[b]pyrazolo[3,4-h][1,6]naphthyridines, and pyrazolo[4′,3′:5,6]pyrido[4,3-d]pyrimidines were synthesized by Friedl?nder condensation of 4-amino-3-methyl-1-phenyl-1H-pyrazolo[3,4-b]pyridine-5-carbaldehyde (o-aminoaldehyde) with active methylene compounds. The o-aminoaldehyde was functionalized to o-aminonitrile and o-aminocarboxamide with malononitrile and cyanoacetamide, respectively, which on condensation with monosubstituted ureas and acetic anhydride, respectively, afforded pyrazolo[3,4-h]pyrimido[4,5-b][1,6]naphthyridines.     

Anionic syntheses of terminally functionalized ethylene oligomers

Synthetic procedures for preparation of terminally functionalized linear ethylene oligomers are described. The preferred synthetic method is anionic oligomerization of ethylene with n-butyllithium–tetramethylethylenediamine and electrophilic substitution of the living oligomer so-formed. Conditions and procedures for subsequent chemistry to elaborate the end groups of these oligomers are described. These procedures afford strictly linear ethylene oligomers which contain a wide variety of end groups and which range in molecular weight from 1000 to 4500 (M_n). The product oligomers were characterized spectroscopically as toluene-d₈ solutions at 110°C using multinuclear NMR, FT-IR, fluorescence, and UV-visible spectroscopies as appropriate. Alternative stepwise approaches to such oligomers are also discussed.     

Kinetics and mechanism of chlorination of toluene and some substituted toluenes by chloramine-T

The kinetics of chlorination of toluene, o-methyl toluene, p-methyl toluene, m-methyl toluene, and m-chlorotoluene by chloramine-T(CAT) in aqueous acetic acid in the presence of HClO₄ have been studied. The reaction is first order with respect to [CAT] as well as [H⁺]. The order with respect to the substrate is unity in the case of toluene and m-chlorotoluene, fractional in the case of o-methyl toluene and p-methyl toluene, and zero order in the case of m-methyl toluene. Nuclear halogenation has been observed with m-methyl toluene, while nuclear and side-chain halogenation for p-methyl toluene and o-methyl toluene, and sidechain halogenation for toluene and m-chlorotoluene are the pathways. An increase in the proportion of acetic acid accelerates the rate. Added acetate ions inhibit the reaction, and added p-toluene sulfonamide causes a pronounced retardation. A mechanism involving AcO⁺HCl as the important electrophile is discussed.     

Synthesis and Structural Studies of Group 2B Transition Metal Complexes with the Bulky Nitrogen Ligand Bis[<Emphasis Type="Italic">N</Emphasis>-(2,6-diisopropylphenyl) imino]acenaphthene

Summary. Group 2B transition metal complexes of bis[N-(2,6-diisopropylphenyl)imino]acenaphthene (o,o-iPr₂C₆H₃-BIAN), namely, [Hg(o,o-iPr₂C₆H₃-BIAN)Cl₂] (1), [Zn(o,o-iPr₂C₆H₃-BIAN)₂](ClO₄)₂ (2), and [Cd(o,o-iPr₂C₆H₃-BIAN)₂](ClO₄)₂ (3) have been synthesized and characterized. In complexes 2 and 3, IR, NMR, and conductivity measurements confirm the coordination of two (o,o-iPr₂C₆H₃-BIAN) ligands to the metal center with two discrete perchlorate anions. X-Ray crystal structure of 1 indicates a distorted tetrahedral geometry with two nitrogen atoms from (o,o-iPr₂C₆H₃-BIAN) ligand and two chloride atoms coordinating to the Hg(II) center.     

A smog chamber and modeling study of the gas phase NOx–air photooxidation of toluene and the cresols

An experimental and modeling study of irradiated toluene–NO_x–air, toluene–benzaldehyde–NO_x–air, and cresol–NO_x–air mixtures at part-per-million concentrations has been carried out. These mixtures were irradiated at 303 ± 1 K in a 5800-liter Teflon-lined, evacuable environmental chamber, with temperature, humidity, light intensity, spectral distribution, and the concentrations of O₃, NO, NO₂, toluene, PAN, formaldehyde, benzaldehyde, o-cresol, m-nitrotoluene, and methyl nitrate beingmonitored as a function of time. For the toluene and toluene–benzaldehyde–NO_x–air runs a variety of initial reactant concentrations were investigated. Cresol–NO_x–air runs were observed to be much less reactive in terms of O₃ formation and NO to NO₂ conversion rates than toluene–NO_x–air runs, with the relative reactivity of the cresol isomers being in the order meta » ortho > para. The addition of benzaldehyde to toluene–NO_x–air mixtures decreased the reactivity, in agreement with previous studies. Alternative mechanistic pathways for the NO_x photooxidations of aromaticsystems in general are discussed, and the effects of varying these mechanistic alternatives on the model predictions for the toluene and o-cresol–NO_x–air systems are examined. Fits of the calculations to most of the experimental concentration–time profiles could be obtained to within the experimental uncertainty for two of the mechanistic options considered. In both cases it is assumed that (1) O₂ adds to the OH–toluene adduct ～75% of the time forming, after a further addition of O₂, a C₇ bicyclic peroxy radical, and (2) this C₇ bicyclic peroxy radical reacts with NO ～75% of the time to ultimately form α-dicarbonyls and conjugated γ-dicarbonyls (e.g., methylglyoxal + 2-butene-1,4-dial) and ～25% of the time to form organic nitrates. The major uncertainties in the mechanisms concern (1) the structure of the bicyclicperoxy intermediate, and (2) the γ-dicarbonyl photooxidation mechanism. Good fits to the o-cresol concentration–time profiles in the toluene–NO_x runs are obtained if it is assumed that o7-cresol reacts rapidly with NO₃ radicals. However, it is observed that the model underpredicts nitrotoluene yields by a factor of ～10, but this is in any case a minor product. It is concluded that further experimental work will be required toadequately validate the assumptions incorporated in the aromatic photooxidation mechanisms presented here.