Synthesis and crystal structures of halogenated oxathiazolones and an unexpected propanamide

The known 1,3,4-oxathiazol-2-ones with crystal structures reported in the Cambridge Structural Database are limited (13 to date) and this article expands the library to 15. In addition, convenient starting materials for the future exploration of 1,3,4-oxathiazol-2-ones are detailed. An unexpected halogenated propanamide has also been identified as a by-product of one reaction, presumably reacting with HCl generated in situ. The space group of 5-[(E)-2-chloroethenyl]-1,3,4-oxathiazol-2-one, C₄H₂ClNO₂S, ( 1 ), is P2₁, with a high Z′ value of 6; the space group of rac-2,3-dibromo-3-chloropropanamide, C₃H₄Br₂ClNO, ( 2 ), is P2₁, with Z′ = 4; and the structure of rac-5-(1,2-dibromo-2-phenylethyl)-1,3,4-oxathiazol-2-one, C₁₀H₇Br₂NO₂S, ( 3 ), crystallizes in the space group Pca2₁, with Z′ = 1. Both of the structures of compounds 2 and 3 are modeled with two-component disorder and each molecular site hosts both of the enantiomers of the racemic pairs (S,S)/(R,R) and (R,S)/(S,R), respectively.     

Extraction and sorption studies using linear polymer chains and model networks

Model networks have been prepared by tetrafunctionally endlinking linear polydimethylsiloxane (PDMS) chains having molecular weights M_n in the range 2000–15,000 g mole^?1. The first series of networks were prepared from mixtures containing known amounts of unreactive linear PDMS chains with molecular weights M_d between 1000 and 16,000 g mole^?1. Rates of extraction were used to estimate diffusion coefficients; as expected, they were found to increase with increase in molecular weight M_c = M_n between crosslinks, but to decrease with increase in M_d. The ease with which all of such a diluent could be removed showed the same dependence on M_c and M_d. A second series of networks was prepared from the same reactive PDMS chains without diluents. Sorption and extraction studies using the same diluents were then carried out. The diffusion coefficients for sorption were found to be in the range (1.7–15.0) × 10^?12 m² s^?1 and depended on both M_c and M_d. The amount of diluent absorbed at equilibrium was between 10 and 70%, which is in good agreement with predictions from the Flory equation for dilation in networks, with account of constraints on crosslink fluctuations.     

Synthesis and properties of eighteen-arm polybutadienes

A series of eighteen-arm regular star polybutadienes with molecular weights between 9.9 × 10⁴ and 1.9 × 10⁶ were prepared and characterized. Evidence is presented for the expanded configuration of the large eighteen-arm stars in a θ solvent. The intrinsic viscosities of the eighteen-arm stars gave g′ = [η]/[η]_l = 0.28₄ in dioxane at 27°C (θ solvent) and 0.22₅ in toluene at 35°C (good solvent). The linear viscoelastic properties of the melts were also determined. The plateau modulus, G_N°, is the same as for linear polybutadiene. The zero-shear viscosities (η₀) and the longest relaxation times (T_max) increase exponentially with the arm molecular weight M_a and are identical to those of four-arm polybutadienes with the same M_a. The zero-shear recoverable compliance (J_e°) increases linearly with molecular weight. v′ in J_e°G_N° = v′N_a, where N_a is the number of entanglements per arm, is 0.95 slightly larger than 0.66 for four-arm polybutadienes. Similarly, g₂ is higher than calculated from the Rouse–Ham theory.     

Synthesis and characterization of polymers and copolymers of vinylruthenocene

Homopolymers of vinylruthenocene and its copolymers with methyl acrylate, styrene, and n-vinylpyrrolidinone have been prepared by free-radical polymerization. No evidence for the electron transfer termination mechanism postulated for polymerization of vinylferrocene was observed. Yields of soluble polymers were 40–90% with M _w (4–25) × 10³ and M _w/M _n = 3.0–13.2. TGA analysis showed little weight loss up to 300°C but rapid decomposition above 300°C. Polyvinylruthenocene is a highly brittle material with T_g above 250°C. Torsional braid analysis of the copolymer samples showed T_g in the range 90–130°C which in some samples increased upon cooling and reheating. Several samples showed weak thermal transitions occurring prior to or following T_g. The rise in T_g upon cooling and reheating is indicative of possible decomposition, crosslinking, or realignment of the polymer chains.     

Organogermane homopolymers and copolymers with organosilane

The first high molecular weight soluble, formable organogermane homopolymer (n-Bu₂Ge)_n was synthesized by the sodium coupling of n-Bu₂GeCl₂ in toluene. Soluble organogermane/organosilane copolymers [(X₂Ge)_x(YZSi)_y]_n were prepared by sodium coupling of X₂GeCl₂ and YZSiCl₂ in different molar ratios (X = n-bu, Ph; Y = n-hexyl, cyclohexyl; Z = Me). Germanium-containing polymers and copolymers with organosilanes are highly absorbing between 300–360 nm, with the absorption maxima dependent on the nature of the substituent and the ratio of X₂Ge:YZSi in the polymer. These polymers are photoactive and display bleaching behavior with photoscission.     

Copper(I) bromide and chloride complexes with urotropine and triethylenediamine: synthesis,crystal structure,and Raman characterization*

Abstract

In the present study, the oxidative dissolution of metallic copper has been explored with the intention to prepare some new complexes with urotropine (hmta) and triethylenediamine (dabco) ligands. All the compounds synthesized were characterized by single-crystal X-ray diffraction and Raman spectroscopy. Reactions performed in a DMSO/CuCl₂?2H₂O mixture resulted in [(μ-Cl)₂Cu^I(hdabco⁺)Cu^I(μ-Cl)(κS-DMSO)]_n and [Cu^ICl(hmta)₂] complexes. Their isostructural bromide analogs [(μ-Br)₂Cu^I(hdabco⁺)Cu^I(μ-Br)(κS-DMSO)]_n and [Cu^IBr(hmta)₂] were prepared by the reaction of elemental copper with respective ligands in a DMSO/CBr₄ mixture. Early interrupted reaction of the copper wire with the DMSO/CBr₄/dabco solution resulted in an appearance of crystals of the [Cu^I₂Br₂(CO)₂(dabco)]_n carbonyl complex on the copper surface. It arises with the participation of in situ formed carbon monoxide. Despite the identical stoichiometry, the crystal structure of the [Cu₂Br₂(CO)₂(dabco)]_n complex is markedly different from that of a known [Cu₂Cl₂(CO)₂(dabco)]_n analog.     

Reaction of Phenylurea and N-Trimethylsilyl-N'-phenylurea with Vanadocene and N-Bromosuccinimide

Phenylurea and N-trimethylsilyl-N'-phenylurea react with vanadocene (Cp₂V) in toluene to give N-(⁵-cyclopentadienyl)vanadio-N'-phenylurea as a major product and Cp₂VN = C = O and aniline as byproducts. The reaction of N-trimethylsilyl-N'-phenylurea with N-bromosuccinimide in THF produces, instead of expected N-phenylureidosuccinimide and bromotrimethylsilane, succinimide and N-(p-bromophenyl)-N-trimethylsilylurea which hydrolyzes to form (p-bromophenyl)urea.     

Synthesis of Some Pyridothienopyrazolopyrimidopyrimidine and Mercaptomethylpyrazolopyrimidine Derivatives

Mercaptomethylpyrazolopyrimidine (2) was synthesized and reacted with ethyl chloroacetate to afford ethyl pyrazolpyrimidinylmethylmercapto acetate ( 3) , which in turn was converted into the corresponding carbohydrazide 4 . Carbohydrazide 4 reacts with a variety of reagents to give different pyrazolopyrimidines ( 5–12 ). Chloromethyl-pyrazolopyrimidine (1) reacts with chloropyridine to give compound 13 , which was subjected in a series of reactions to give new compounds 14–20 .     

Di‐ and triphenylacetate complexes of yttrium and europium

The significant variety in the crystal structures of rare‐earth carboxylate complexes is due to both the large coordination numbers of the rare‐earth cations and the ability of the carboxylate anions to form several types of bridges between rare‐earth metal atoms. Therefore, these complexes are represented by mono‐, di‐ and polynuclear complexes, and by coordination polymers. The interaction of LnCl₃(thf)_x (Ln = Eu or Y; thf is tetrahydrofuran) with sodium or diethylammonium diphenylacetate in methanol followed by recrystallization from a DME/THF/hexane solvent mixture (DME is 1,2‐dimethoxyethane) leads to crystals of the non‐isomorphic dinuclear complexes tetrakis(μ‐2,2‐diphenylacetato)‐κ⁴O:O′;κ³O,O′:O′;κ³O:O,O′‐bis[(1,2‐dimethoxyethane‐κ²O,O′)(2,2‐diphenylacetato‐κ²O,O′)europium(III)], [Eu(C₁₄H₁₁O₂)₆(C₄H₁₀O₂)₂], (I), and tetrakis(μ‐2,2‐diphenylacetato)‐κ⁴O:O′;κ³O,O′:O′;κ³O:O,O′‐bis[(1,2‐dimethoxyethane‐κ²O,O′)(2,2‐diphenylacetato‐κ²O,O′)yttrium(III)], [Y(C₁₄H₁₁O₂)₆(C₄H₁₀O₂)₂], (II), possessing monoclinic (P2₁/c) symmetry. The [Ln(Ph₂CHCOO)₃(dme)]₂ molecule (Ln = Eu or Y) lies on an inversion centre and exhibits three different coordination modes of the diphenylacetate ligands, namely bidentate κ²O,O′‐terminal, bidentate μ₂‐κ¹O:κ¹O′‐bridging and tridentate μ₂‐κ¹O:κ²O,O′‐semibridging. The terminal and bridging ligands in (I) are disordered over two positions, with an occupancy ratio of 0.806 (2):0.194 (2). The interaction of EuCl₃(thf)₂ with Na[Ph₃CCOO] in methanol followed by crystallization from hot methanol produces crystals of tetrakis(methanol‐κO)tris(2,2,2‐triphenylacetato)‐κ⁴O:O′;κO‐europium(III) methanol disolvate, [Eu(C₁₉H₁₅O₂)₃(CH₃OH)₄]·2CH₃OH, (III)·2MeOH, with triclinic (P) symmetry. The molecule of (III) contains two O,O′‐bidentate and one O‐monodentate terminal triphenylacetate ligand. (III)·2MeOH possesses one intramolecular and four intermolecular hydrogen bonds, forming a [(III)·2MeOH]₂ dimer with two bridging methanol molecules.     

Phosphono-substituted isoindolines and indoles from 2,3- and 2,4-benzoxazin-1-ones

Reactions of 2,3-benzoxazinone 1 and 2,4-benzoxazinone 2 , with trialkyl phosphites 3a–c provide access to new phosphono-substituted isoindolines 6a–f and indoles 19a–e , respectively. Phosphono-substituted 2,3-benzoxazines 5a–c were also obtained in the first reaction. Bisisoindolinylidene ( 7 ) was, however, isolated in low yields when 1 was heated with triethyl or triisopropyl phosphite at 100deg;C whereas at 170deg;C 7 was obtained as the major product (∼53%). On the other hand, the reaction of 1 or 2 with dialkyl phosphonates 4a–c proceeded in the presence of aqueous solution of NaOH (5%) to give the respective alkylated product 14a–c or 20a–c . © 2003 Wiley Periodicals, Inc. 15:77–84, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/.10216     

Experimental determination of the electron elastic backscattering probability and the surface excitation parameter for Si,Ni, Cu and Ag at 0.5 and 1 keV energies

Electron spectra are generally presented in arbitrary units. The experimental elastic peak intensity I_espec(E) is determined by the elastic backscattering probability I_e(E) of electrons backscattered elastically within the solid angle of the spectrometer. The experimental elastic peak I_espec(E) is converted to I_e(E) backscattering probability using our new procedure based on the Goto i_e(E) elastic backscattering current database. The elastic backscattering probability I_c(E) was calculated applying the EPESWIN software of Jablonski. I_e(E) < I_c(E) due to the surface losses of electrons, characterized by the surface excitation parameter P_se (SEP). P_se(E) was determined experimentally using the Goto database and the relationship of Tanuma. Our new procedure is applied to angular‐resolved (AREPES) spectra of Jablonski and Zemek presented in arbitrary units. In their AREPES experiments, the experimental elastic peak intensity I_espec = I_e(E, α_d, ΔΩ) was measured at α_d angle of detection (35–74°) with a small HSA, with ΔΩ solid angle. The experimental value at 42° $I_{e}(E, {\it{42}}\deg{\hbox{}}, {\Delta}\Omega)$ was converted to probability with the Goto database. It was corrected with a SEP parameter P_se, determined by trial and error method for Si, Ni, Cu and Ag for E = 0.5 and 1 keV primary energies. Copyright © 2010 John Wiley & Sons, Ltd.     

Low- and high-molecular-weight polyacetylenes: Synthesis,characterization, and thermal isomerization

Procedures for the synthesis of polyacetylene ([CH]_x) with M _n (number average molecular weight) from 400 to about 10⁶ have been developed. This probably represents the largest range of molecular weight (MW) obtainable for a given monomer by a single initiator system. The catalyst residue level in [CH]_x can be significantly reduced by acidic-methanol purification. The very low MW polymer L-[CH]_x (polyacetylenes with M _n 400–500), has the same cis crystal structure as the higher MW polymers but is less ordered along the c-axis. It is isomerized to the trans material with apparently a more compact unit cell than high MW polymers. There is annealing of crystallite which increases the longitudinal order during thermal isomerization. This process occurs more readily and with lower activation energy in L-[CH]_x than for polymers with higher MW. Isomerization of high MW polymers tends to trap cis units which can result in degradation as evidenced by the formation of sp³ carbon vibrations in IR spectra. This is true even for L-[CH]_x after prolonged heating. The results render credence to the proposal based on anamalous resonance Raman scattering profile that there can be very short trans segments in thermally isomerized trans-[CH]_x.     

Preparation and X-ray structures of complexes of 18-membered crown ethers with polyfunctional guests: Urea and (O-alkyliso)uronium salts

The preparation and X-ray structure determinations of six complexes of urea and (O-n-butyliso)uronium salts with crown ethers are presented. Urea forms isostructural 5:1 adducts with 18-crown-6 (1) and aza-18-crown-6 (2), in which two urea molecules are each hydrogen bonded to two neighbouring hetero atoms of the macroring. The remaining urea molecules form two-dimensional layers alternating with crown ether layers. In both complexes the macroring has theg ⁺ g ⁺ a ag ^– a ag ^– a g ^– g ^– a ag ⁺ a ag ⁺ a conformation withC _i symmetry. In the solid 1:1 complex of O-n-butylisouronium picrate with 18-crown-6 (3) two types of conformations of the macroring were observed: theg ⁺ g ⁺ a ag ^– a ag ⁺ a ag ^– g ^– ag ^– a ag ⁺ a conformation with approximateC _m symmetry and to a lesser extent theg ⁺ g ⁺ a ag ^– a ag ⁺ a g ⁺ g ⁺ a ag ^– a ag ⁺ a conformation with approximateC ₂ symmetry. Both conformations allow the guest to form three hydrogen bonds to the macrocyclic host. Three complexes of 18-crown-6 and uronium salts have been prepared and characterized by X-ray crystallography. The 1:1 complexes with uronium nitrate (4) and uronium picrate (5) both exhibit the sameC ₂ conformation and the same hydrogen bonding scheme as in the least occupied form of the previous complex. A 1:2 complex with uroniump-toluenesulphonate (6) has a different hydrogen bonding scheme (two hydrogen bonds per cation to neighbouring oxygen atoms of the macroring) and a different conformation of the host molecule (theag ⁺ a ag ^– a ag ⁺ a ag ^– a ag ⁺ a ag ^– a conformation with almostD _3d symmetry). An attempt to prepare a solid uronium nitrate complex with diaza-18-crown-6 in the same way as the 18-crown-6·uronium nitrate (1:1) complex did not yield the expected result. Instead X-ray analysis revealed that the uronium ion is dissociated, resulting in the nitrate salt of the diprotonated diaza crown ether (7). Supplementary Data relating to this article are deposited with the British Library as Supplementary Publication No. SUP 82058 (26 pages).     

Radical and anionic homopolymerization of maleimide and N-n-butylmaleimide

The rate of homopolymerization of maleimide has been measured in dimethylformamide solution at 60°C. in the presence of azobisisobutyronitrile; it has been compared to that of N-n-butylmaleimide. The overall rates of polymerization are equal to R_p = k[M]^1.1–1.2 [In]^0.8 for maleimide, and R_p = k'[M] [In]^0.5 for the N-substituted imide. The difference of behavior has been interpreted on the basis of an intramolecular tautomery of the terminal group of the maleimide growing chain and the formation of a resonance-stabilized succinimidyl radical. The relative ease of polymerization of these monomers and of maleic anhydride has been discussed. In the presence of sodium tert-butoxide at 20°C. in dimethylformamide solutions, maleimide polymerizes with hydrogen isomerization. The percentage of N-substituted isomerized units was evaluated at 70–75% by measurement of the rate of hydrolysis in 0.005N sodium hydroxide and comparison with succinimide and N-butylsuccinimide. N-n-butylmaleimide undergoes ring opening together with anionic polymerization in the presence of sodium tert-butoxide at 20°C. and butyllithium at -40°C. Unlike the radical-initiated polymerization, it was impossible to obtain anionic copolymers of maleimide and N-butylmaleimide with acrylonitrile and methyl methacrylate.     

Derivatives Of ditraizinylamine and tritriazinylamine

2-Arylamino-4,6-dichloro-s-triazine reacts with cyanuric chloride in the presence of alkali to yield N,N-bis(4,6-dichloro-s-triazin-2-yl)-arylamine. In like manner, 2-substituted o-chloro-, p-chloro-, o-nitro- and p-carbomethoxyphenylamino-4,6-dimethoxy-s-triazines react with cyanuric chloride to yield the corresponding 4,6-dichloro-s-triazin-2-yl-4′,6′-dimethoxy-s-triazin-2′-ylaryl-amine, while anilino-, p-toluidino, o- and p-methoxyphenylamino and o-carbomethoxyphenylamino derivatives did not. The reaction of cyanuric chloride with 2,4-dichloro-6-ethylamino-s-triazine in the presence of alkali yields the condensation product of the ditriazinylamine type and the reaction of cyanuric chloride with ammonia yields N,N-bis(4,6-dichloro-s-triazin-2-yl)- or tris(4,6-dichloro-s-triazin-2-yl)amine.     

Copolymerization of fluorinated acrylic monomers with p-vinylphenol and hydroxyethyl methacrylate

Copolymers of p-vinylphenol were prepared in bulk with heptafluorobutyl and pentadecafluorooctyl acrylates and trifluoroethyl, hexafluoroisopropyl, heptafluorobutyl, octafluoropentyl and pentadecafluorooctyl methacrylates using azobisisobutyronitrile as the initiator in sealed tubes. Intrinsic viscosities of the copolymers ranged from 0.44 to 1.85. Monomer reactivity ratios for copolymers of trifluoroethyl methacrylate (M₁) were: with hydroxyethyl methacrylate (M₂), r₁ = 0.47, r₂ = 1.0; with methyl methacrylate (M₂), r₁ = 0.82, r₂ = 0.50; with styrene (M₂), r₁ = 0.29, r₂, = 0.20; and with p-vinylphenol (M₂), r₁ = 0.096, r₂ = 1.5. Q and e values of trifluoroethyl methacrylate were 1.30 and 0.92, respectively. Monomer reactivity ratios of octafluoropentyl methacrylate (M₁) were: with styrene (M₂), r₁ = 0.26, r₂ = 0.20; and with p-vinylphenol, r₁ = 0.21, r₂ = 1.5. Q and e values for octafluoropentyl methacrylate were 1.27 and 0.92, respectively. Critical surface tensions of the homopolymers ranged from 17.9 to 14.8 dyn/cm. A copolymer of hexafluoro-i-propyl methacrylate and p-vinylphenol exhibited a critical surface tension of 16.5 dyn/cm.     

Conformational analysis of 2-halocyclopentanones by NMR and IR spectroscopies and theoretical calculations

The conformational isomerism of 2-chlorocyclopentanone and 2-bromocyclopentanone has been determined through the solvent dependence of the ¹H NMR ³J_HH coupling constants, theoretical calculations and infrared data, using the solvation theory for the treatment of NMR data. In 2-chlorocyclopentanone, the energy difference (E_Ψ-e − E_Ψ-a), in the isolated molecule at B3LYP level of theory, between the pseudo-equatorial (Ψ-e) and pseudo-axial (Ψ-a) conformers is 0.42 kcal mol⁻¹, which decreases in CCl₄ and in acetonitrile solutions, in good agreement with infrared data (ν_CO), despite the uncertainties of the latter method. The conformational equilibrium for 2-bromocyclopentanone is also between the Ψ-e and Ψ-a conformations, with an energy difference (E_Ψ-e − E_Ψ-a), in the isolated molecule at B3LYP level of theory, is 0.85 kcal mol⁻¹ which decreases in CCl₄ and in acetonitrile solutions, also in good agreement with infrared data.     

Benzofuranyl-pyran-2-ones, -pyridazines,and -pyridones from naturally occurring furochromones (visnagin and khellin)

The novel and versatile enaminones 2a,b were synthesized by treatment of visnaginone methyl ether 1a or khellinone methyl ether 1b with N,N-dimethylformamide dimethylacetal. They were reacted with hippuric acid or N-acetylglycine to yield benzofuran-5-yl-2H-pyran-2-ones 3a–d . The reaction of 2a,b with cyanoacetamide and malononitrile dimer in sodium ethoxide gave benzofuran-5-yl-pyridones 4a,b and [benzofuran-5-yl-1H-pyridine-2-ylidene] malononitrile 5a , respectively. Refluxing 2a,b with hydrazine hydrate or with hydroxyla- mine afforded benzofuran-5-yl-1H-pyrazoles 6a,b and benzofuran-5-yl-isoxazoles 7a,b , respectively. Moreover, 2a,b coupled with aryl diazonium salt in the presence of sodium hydroxide to yield 3-(benzofuran-5-yl)-2-aryl-hydrazono-3-oxo-propanals 8a,b which were excellent precursors for the synthesis of pyridazines 9–12 . © 2003 Wiley Periodicals, Inc. 15:85–91, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.10219     

Structure and morphology development in syndiotactic polypropylene during isothermal crystallization and subsequent melting

Structure and morphology development during the isothermal crystallization and subsequent melting of syndiotactic polypropylene (sPP) was studied with differential scanning calorimetry (DSC), time‐resolved simultaneous small‐angle X‐ray scattering (SAXS), and wide‐angle X‐ray diffraction (WAXD) methods with synchrotron radiation. The morphology of sPP isothermally crystallized at 100 °C for 3 h was also characterized with transmission electron microscopy (TEM). Time‐ and temperature‐dependent parameters such as the long period (L), crystal lamellar thickness (l_c), amorphous layer thickness (l_a), scattering invariant (Q), crystallinity (X_c), lateral crystal sizes (L₂₀₀ and L₀₁₀), and unit cell dimensions (a and b) were extracted from the SAXS and WAXD data. Results indicate that the decreases in L and l_c with time are probably due to the formation of thinner crystal lamellae, and the decreases in a and b are due to crystal perfection. The changes in the morphological parameters (Q, X_c, L, and l_c) during subsequent melting exhibited a two‐stage process that was consistent with the multiple melting peaks observed in DSC. The two high‐temperature peaks can be attributed to the melting of primary lamellae (at lower temperatures) and recrystallized lamellae (at higher temperatures). An additional minor peak, located at the lowest temperature, was also visible and was related to the melting of thin and defective secondary lamellae. TEM results are consistent with the SAXS data, which supports the assignment of the larger value (l₁) from the correlation function analysis as l_c. WAXD showed that the thermal expansion was greater along the b axis than the a axis during melting. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2982–2995, 2001     

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.