Reaction of α,α,ω-trichloroalkenes with 1,1,1-trichloroethane and 1,1,1,3-tetrachloropropane,accompanied by rearrangement of radicals

Conclusions In the reaction of CCl₃CH₃ with CCl₂=CHCH₂CH₂CH₂Cl, and of CCl₃CH₂CH₂Cl with CCl₂= CHCH₂Cl, initiated by Fe(CO)₅+DMF, the main addition products are respectively compounds of structure HCCl₂CH(CCl₂CH₃)CH₂CH₂CHCl₂ and HCCl₂CH(CCl₂CH₂CHCl₂)CH₂C1. The formation of these compounds was explained by the isomeriza'tion of the radical-adducts CCl₂CH(CCl₂CH₃)CH₂CH₂CH₂Cl and CCl₂CH(CCl₂CH₂CH₂Cl)CH₂Cl, with migration of a hydrogen atom from the CH₂Cl groups found in the 5 position to the radical center.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 8, pp. 1857–1861, August, 1980.     

Reactions of methyl radicals with acetaldehyde and acetaldehyde-d1. II. BEBO calculations of the temperature dependence of the rate constants

The BEBO method was used to calculate the kinetic isotope effect for formyl-hydrogen abstraction from acetaldehyde by methyl radicals. The calculated isotope effect and experimental ratios of the rate constants obtained at 785°K for the reactions of CH₃ with CH₃CHO and CH₃CDO, together with the theoretical temperature dependence of the specific rates (as formulated by the BEBO theory), were used to obtain rate constants for the steps CH₃ + CH₃CHO → CH₄ + CH₃CO (2a), CH₃ + CH₃CHO → CH₄ + CH₂CHO (2b), and CH₃ + CH₃CDO → CH₃D + CH₃CO (1a) between 298 and 1224°K. It was shown that the curvature apparent in the Arrhenius plot of the rate coefficient k₂ reported for the reaction of methyl radicals with acetaldehyde in the temperature range of 298–1224°K is caused both by the simultaneous contribution of steps (2a) and (2b) to methane formation, and by the curvature in the Arrhenius plots of the two elementary rate constants themselves. The predicted curve agrees well with the experimental data, especially if the tunneling correction is applied.     

Theoretical investigation on mechanism for OH-initiated oxidation of CH2=C(CH3)CH2OH

The mechanism of the gas-phase reaction OH with CH₂=C(CH₃)CH₂OH (2-methyl-2-propen-1-ol) has been elucidated using high-level ab initio method, i.e., CCSD(T)/6-311++g(d,p)//MP2(full)/6-311++g(d,p). Various possible H-abstraction and addition–elimination pathways are identified. The calculations indicate that the addition–elimination mechanism dominates the OH+MPO221 reaction. The addition reactions between OH radicals and CH₂=C(CH₃)CH₂OH begin with the barrierless formation of a pre-reactive complex in the entrance channel, and subsequently the CH₂(OH)C(CH₃)CH₂OH (IM1) and the CH₂C(OH)(CH₃)CH₂OH (IM2) are formed by OH radicals’ electrophilic additions to the double bond. IM1 can easily rearrange to IM2 via a 1,2-OH migration. Subsequently, rearrangement of IM2 to form (CH₃)₂C(OH)CH₂O (IM11) followed by dissociation to HCHO + (CH₃)₂COH (P21) is the most favorable pathway. The decomposition of IM2 to CH₂OH + CH₂=C(OH)CH₃ (P16) is the secondary pathway. The other pathways are not expected to play any important role in forming final products.     

1,2-Eliminations from (CH3)2NH+CH2CH3 and (CH3)2NH 2+ : Guided dissociations

1,2-Eliminations are a varied and extensive set of dissociations of ions in the gas phase. To understand better such dissociations, elimination of CH₂=CH₂ and CH₃CH₃ from (CH₃)₂NH⁺CH₂CH₃ (1) and of CH₄ from (CH₃)₂NH₂⁺ are characterized by quantum chemical calculations. Stretching of the CN bond to ethyl is followed by shift of an H from methyl to the bridging position in ethyl and then to N to reach (CH₃)₂NH₂⁺ + CH₂=CH₂ from 1. CH₃CH₃ elimination by H-transfer to C₂H₅⁺ to form CH₃NH⁺=CH₂ + CH₃CH₃ also takes place. (CH₃)₂NH₂⁺ eliminates methane by CN bond extension followed by β-H-transfer to give CH₂=NH⁺ + CH₄. Low-energy reactions resembling complex-mediated 1,2-eliminations occur and constitute a hitherto largely unrecognized type of reaction. As in many complex-mediated reactions, these reactions transfer H between incipient fragments. They are distinguished from complex-mediated processes by the fragments not being able to rotate freely relative to each other near the transition state for reaction, as they do in complexes. Most 1,2-eliminations are ion-neutral complex-mediated, occur by the just described lower energy reactions, have 1,1-like transition states, or utilize highly asynchronous 1,2 transition states. All of these avoid synchronized 1,2-transition states that would violate conservation of orbital symmetry.     

Thermodynamics of Bromo-Adamantane and Carbon Tetrabromide Under Pressure

Excess molar volumes at 298.15 K of the ternary system {CH₃(CH₂)₂CO₂(CH₂)₃CH₃+ CH₃(CH₂)₇OH+CH₃(CH₂)₆CH₃} and the binary mixtures {CH₃(CH₂)₂CO₂(CH₂)₃CH₃+ CH₃(CH₂)₇OH}, {CH₃(CH₂)₂CO₂(CH₂)₃CH₃+CH₃ (CH₂)₆CH₃} and {CH₃(CH₂)₇OH+ CH₃(CH₂)₆CH₃} were determined using an Anton Paar DMA 60/602 densimeter. All experimental values were compared with the results obtained with empirical expressions for estimation of the ternary properties from the binary data. Variable-degree polynomials were fitted to the results. This revised version was published online in July 2006 with corrections to the Cover Date.     

Darstellung und Eigenschaften von 3-(N,N-Dimethylamino)propyl-Verbindungen des Thalliums

Preparation and Properties of 3-(N,N-Dimethylamino)propyl Thallium Compounds TlCl₃ reacts with Me₂NCH₂CH₂CH₂Li in molar ratio 1:2 with formation of (Me₂NCH₂CH₂CH₂)₂TlCl ( 1 ) which can be transfered with MeLi into (Me₂NCH₂CH₂CH₂)₂TlMe ( 2 ) and with excess of Me₂NCH₂CH₂CH₂Li into (Me₂NCH₂CH₂CH₂)₃Tl ( 3 ) respectively. Comproportionation of 1 with TlCl₃ yields rather instable Me₂NCH₂CH₂CH₂TlCl₂ ( 4 ) from which Me₂NCH₂CH₂CH₂TlMe₂ ( 5 ) can be obtained by alkylation with MeLi. 1–3 and 5 were characterized by elemental analysis, mass spectra, ¹H- and ¹³C-n.m.r. spectra.     

Synthesis,Thermal Behavior,and Dehydrogenation Kinetics Study of Lithiated Ethylenediamine

The lithiation of ethylenediamine by LiH is a stepwise process to form the partially lithiated intermediates LiN(H)CH₂CH₂NH₂ and [LiN(H)CH₂CH₂NH₂][LiN(H)CH₂CH₂N(H)Li]₂ prior to the formation of dilithiated ethylenediamine LiN(H)CH₂CH₂N(H)Li. A reversible phase transformation between the partial and dilithiated species was observed. One dimensional {Li_nN_n} ladders and three‐dimensional network structures were found in the crystal structures of LiN(H)CH₂CH₂NH₂ and LiN(H)CH₂CH₂N(H)Li, respectively. LiN(H)CH₂CH₂N(H)Li undergoes dehydrogenation with an activation energy of 181±8 kJ mol^?1, whereas the partially lithiated ethylenediamine compounds were polymerized and released ammonia at elevated temperatures. The dynamical dehydrogenation mechanism of the dilithiated ethylenediamine compounds was investigated by using the Johnson‐Mehl‐Avrami equation.     

Competing dissociation of and bond formation between CH3CHOH+ and .CH2CH3 formed by bimolecular processes

The C₄H₁₀O^.+ potential energy surface was accessed at several energies through different ion/molecule reactions. Reaction of CH₃CH^.+₃ with CH₃CHO and CH₃CHO^.+ with CH₃CH₃ gave predominantly CH₃CHOH⁺ +^. CH₂CH₃ and small amounts of CH₃CH₂CHOH⁺ +^. CH₃. CH₃CH^.+₃ also produced a small amount of CH₃CHO⁺CH₃ +^. CH₃ upon reaction with CH₃CHO. CH₂ = CHOH^. + did not react with CH₃CH₃. CH₃CH₂OH^. + reacted CH₂ = CH₂ and CH₂ = CH^.+₂ with CH₃CH₂OH to produce CH₃CH₂OH⁺₂ and CH₃CHOH⁺, but only the second pair of reactants produced detectable C₃H₇O⁺ ions. CH₃CH₂CHO.+⁺CH₄ produced only CH₃CH₂CHOH⁺. In all of the reactions examined, initial proton or H-transfer was much more often followed by simple dissociation than by CC bond formation or multiple H-transfers. This contrasts with the metastable decompositions of ionized 2-butanol, in which elimination of ethane and methane through the complexes [CH₃CHOH^+.CH₂CH₃] and [CH₃CH₂CHOH^+.CH₃] are important processes. This contrast is attributed to the ion/molecule reactions taking place in a higher energy regime than the metastable decompositions.     

Substitutionsreaktionen mit Schwefeldiimiden

Substitution Reactions with Sulphur Diimides Substituted sulphur diimides are obtained by the reactions of (CH₃)₃Si? N?S?N? Si(CH₃)₃ with CH₃SO₂Cl and CCl₃SCl or with P₂O₃F₄ and (CH₃)₃Si? N?S?N? SN(CH₃)₂. S₄N₄ reacts with (CH₃)₂Si[N(CH₃)₂]₂ to from (CH₃)₂Si(N(CH₃)₂)? N?S?N? SN(CH₃)₂ while S₃N₂Cl₂ yields (CH₃)₂Si(Cl)? N?S?N? SN(CH₃)₂. It is possible to substitute the chlorine atom by diethylamine in the last compound. The new compounds are intermediates for the syntheses of cyclic sulphur-nitrogen compounds. They were characterized by mass-, ir-, ¹H-nmr spectra and elemental analysis.     

Wetting properties of bis(trifluoromethyl)carbinyl acrylate polymers

A series of bis(trifluoromethyl)carbinyl acrylate monomers [Y-C(CF₃)₂ O? CO? CH?CH₂] in which Y is CH₃, CH₃CH₂, CH₃CH₂CH₂, CH₃CH₂CH₂CH₂, C₆H₅, H, F, CF₃, N₃, CN, and CH₃OCH₂CH₂O, was prepared. Polymers were easily prepared from all of these monomers except where Y = CN, wherein a variety of initiation methods failed to produce high molecular polymer. Wettabilities of the polymer films were examined by means of contact angle measurements by using n-alkane test liquids and water. Values of the dispersion force contribution (γs^d) and the polar force contribution (γs^p) to the solid surface energy were calculated by employing both geometric and harmonic mean approximations. Values of γs^d calculated by either method agreed well with γ_c (critical surface tension) values determined graphically from contact angle data employing n-alkane test liquids, confirming the suggestion that γ_c is an approximate measure of the dispersion force contribution to solid surface energy. Values of γs_d ranged from 15 dyne/cm (Y = F or CF₃) to 25 dyne/cm (Y = C₆H₅). Values of the polar force contribution to solid surface energy (γs^p) varied from 0.6 dyne/cm (Y = CH₃CH₂CH₂CH₂) to 3.4 dyne/cm (Y = CH₃OCH₂CH₂O) when calculated by the geometric mean equation. The values of γs^p obtained from the harmonic mean equation followed the same trend upon varying substituents, but were larger in value, ranging from 2.9 dyne/cm (Y = CH₃CH₂CH₂CH₂) to 7.5 dyne/cm (Y γ CH₃OCH₂CH₂O).     

Bis(fluoroalkyl)acrylic and methacrylic phosphate monomers, their polymers and some of their properties

Ten fluoromonomers of structure (R_FO)₂P(O)OCH₂CH₂OC(O)CRCH₂ were made in 30-64% yield by treating the chloridates (R_FO)₂P(O)Cl with HOCH₂CH₂OC(O)CRCH₂ in chloroform in the presence of triethylamine [R_F=CF₃CH₂, C₂F₅CH₂, C₃F₇CH₂, C₄F₉CH₂, C₄F₉CH₂CH₂ or C₆F₁₃CH₂CH₂; R  H or Me]. The chloromonomer (CCl₃CH₂O)₂P(O)OCH₂CH₂OC(O)CHCH₂ was obtained analogously in 29% yield. Polymerisation of the acrylate monomers, but not the methacrylate monomers, could be effected using α-azoisobutyronitrile as a radical initiator. Acrylic polymers having CF₃CH₂O, CCl₃CH₂O and C₆F₁₃CH₂CH₂O side-chains were obtained as translucent rubbers. Specimens of cotton fabric were treated with solutions of the polymers, and average water and oil repellency ratings measured. Fabric coated with the polymer with the C₆F₁₃CH₂CH₂O side-chain afforded protection from penetration of the test liquids. Treated fabrics were subjected to the limiting oxygen index (LOI) test according to BS EN ISO 4589-2 (1999): this test determines the point at which a material just burns in a volumetric flow of oxygen and nitrogen. The treated fabrics were more fire-resistant (LOI 22-29%) than the untreated fabric (LOI 18%). Fabric coated with the CCl₃CH₂O-based polymer can be considered fire-retardant (LOI 29%). The fluoromonomers were tested for anti-acetylcholinesterase activity and were found to be poor enzyme inhibitors; they are predicted to possess low acute toxicity.     

New cyclic phosphonium salts derived from the reaction of phosphine-aldehydes with acid

Various cyclic phosphonium structures are formed in high yield by the deprotection of unstable phosphine-aldehydes in acidic solution. When there is a methylene spacer between the phosphine and the aldehyde, a phosphonium ion [PHR₂CH₂CH(OEt)₂]Br₂, R=iPrOH, Et is obtained. Reaction of these phosphonium salts with water produces the dimers [-PR₂CH₂CH(OH)-]₂[Br]₂ R = iPr, Et. When there is an ethylene spacer as in PPh₂CH₂CH₂CH(OCH₂CH₂O), a remarkable tetramer with a 16-membered ring [-PPh₂CH₂CH₂CH (OH)-]₄[Cl]₄ forms as one diastereomer in hydrochloric acid solution. Reaction of HCl with the protected phosphine-aldehyde with a propylene spacer (PPh₂CH₂CH₂CH₂CH(OCH₂CH₂O)) results in the formation of the monomeric phosphonium salt [-PPh₂ CH₂CH₂CH₂CH(OH)-]Cl with a 5-membered ring. Solid state structures of different ring types were determined using X-ray diffraction experiment.     

COPOLYMERIZATION OF ETHYLENE AND PROPYLENE WITH CpCH2CH2CH=CH2)2MCl2(M=Zr,Hf)AND Cp2ZrCl2 CATALYSTS

(CpCH_2CH_2CH = CH_2)_2MCl_2(M=Zr, Hf)/MAO and Cp_2ZrCl_2/MAO (Cp=cyclopentadienyl; MAO=methylaluminoxane) catalyst systems have been compared for ethylene copolymerization to investigate the influence of theligand and transition metal on the polymerization activity and copolymer properties. For both CH_2CH_2CH=CH_2 substitutedcatalysts the catalytic activity decreased with increasing propene concentration in the feed. The activity of the hafnocenecatalyst was 6～8 times lower than that of the analogous zirconocene catalyst, ~(13)C NMR analysis showed that the copolymerobtained using the unsubstituted catalyst Cp_2ZrCl_2 has greater incorporatien of propene than those produced byCH_2CH_2CH=CH_2 substituted Zr and Hf catalysts. The melting point, crystallinity and the viscosity-average molecularweight of the copolymer decreased with an increase of propenc concentration in the feed. Both CH_2CH_2CH= CH_2 substitutedZr and Hf catalysts exhibit little or no difference in the melting point and crystallinity of the produced copolymers. However,there are significant differences between the two zirconocene catalysts. The copolymer produced by Cp_2ZrCl_2 catalyst havemuch lower T_m and X_c than those obtained with the (CpCH_2CH_2CH=CH_2)_2ZrCl_2 catalyst. The density and molecular weightof the copolymer decreased in the order: (CpCH_2CH_2CH=CH_2)_2HfCl_2>(CpCH_2CH_2CH=CH_2)_2ZrCl_2>Cp_2ZrCl_2. The kineticbehavior of copolymerizaton with Hf catalyst was found to be different from that with Zr catalyst.     

Electron Spin Resonance of α-(Alkoxycarbonyl)alkyl Radicals in Solution

High-resolution ESR. spectra of the radicals CH₂COOR, CH₃CHCOOR and (CH₃)₂CCOOR with R?CH₃, CH₂CH₃, CH(CH₃)₂ and C(CH₃)₃ in liquid solution confirm planar energy-minimum structures with substantial barriers to internal rotation about the ?, CO-bonds (?40 kJ/mol) and partial π-electron delocalization. The assignments of coupling constants to protons in isomeric positions and the conclusions on radical structures are supported by INDO-calculations.     

Synthese von methyldihalogenarsinen CH3AsXY mit verschiedenen halogenen XY

The reactions of the methylhalogenodimethylaminoarsines CH₃As-[N(CH₃)₂]X (X  F, Cl, Br, I) with HY (Y = Cl, Br) yield the methyldihalogenoarsines CH₃AsXY. The compounds CH₃As[N(CH₃)₂]X are prepared by the reactions of CH₃AsCl₂ with HN(CH₃)₂, CH₃As[N(CH₃)₂]₂ with HX (X = Cl, Br) and by exchange reactions between CH₃As[N(CH₃)₂]₂ and CH₃AsX₂ (X = F, Cl, Br, I).     

Lithiation of the Tin-containing Sulfone Me3SnCH2CH2CH2SO2C6H4CH3-4

The tin-containing sulfide Me₃Sn(CH₂)₃-S-C₆H₅CH₃-4 obtained by photoaddition of 4-toluene- thiol to allyltrimethyltin was oxidized with hydrogen peroxide to synthesize the tin-containing sulfone Me₃Sn(CH₂)₃-SO₂-C₆H₄CH₃-4, the tin and sulfur atoms in which are separated by a trimethylene bribge. Treatment of the sulfone with butyllithium gave a first tin-containing lithium salt having a red-brown color. The exchange reaction of this salt with methyl iodide resulted in formation of two new isomeric tin-containing sulfones Me₃SnCH₂CH₂CH(CH₃)-SO₂-C₆H₄CH₃ and Me₃Sn(CH₂)₃-SO₂-C₆H₄CH₂CH₃ identified by ^1HNMR spectroscopy. The latter result implies that the tin-containing sulfone is lithiated both by the methylene group adjacent to the sulfonyl group and by the toluene methyl group.     

Reactions of ionized dibutyl ether

The reactions of ionized di-n-butyl ether are reported and compared with those of ionized n-butyl sec-butyl and di-sec-butyl ether. The main fragmentation of metastable (CH₃CH₂CH₂CH₂)₂O^+. is C₂H₅? loss (?85%), but minor amounts (2–4%) of CH₃?, C₄H₇?, C₄H₉?, C₄H₁₀ and C₄H₁₀O are also eliminated. In contrast, C₂H₅? elimination is of much lower abundance (20 and 4%, respectively) from metastable CH₃CH₂CH₂CH₂OCH(CH₃)CH₂CH₃^+. and [CH₃CH₂(CH₃)CH]₂O^+., which expel mainly C₂H₆ and CH₃? (35–55%). Studies on collisional activation spectra of the C₆H₁₃O⁺ oxonium ions reveal that C₂H₅? loss from (CH₃CH₂CH₂CH₂)₂O^+. gives the same product, (CH₃CH₂CH₂CH₂ ⁺O?CHCH₃) as that formed by direct cleavage of CH₃CH₂CH₂CH₂OCH(CH₃)CH₂CH₃^+.. Elimination of C₂H₅? from (CH₃CH₂CH₂CH₂)₂O^+. is interpreted by means of a mechanism in which a 1,4-H shift to the oxygen atom initiates a unidirectional skeletal rearrangement to CH₃CH₂CH₂CH₂OCH(CH₃)CH₂CH₃^+., which then undergoes cleavage to CH₃CH₂CH₂CH₂⁺O?CHCH₃ and C₂H₅?. Further support for this mechanism is obtained from considering the collisional activation and neutralization-reionization mass spectra of the (C₄H₉)₂O^+. species and the behaviour of labelled analogues of (CH₃CH₂CH₂CH₂)₂O^+.. The rate of ethyl radical loss is suppressed relative to those of alternative dissociations by deuteriation at the γ-position of either or both butyl substituents. Moreover, C₂H₅? loss via skeletal rearrangement and fragmentation of the unlabelled butyl group in CH₃CH₂CH₂CH₂OCH₂CH₂CD₂CH₃^+. occurs approximately five times more rapidly than C₂H₄D? expulsion via isomerization and fission of the labelled butyl substituent. These findings indicate that the initial 1,4-hydrogen shift is influenced by a significant isotope effect, as would be expected if this step is rate limiting in ethyl radical loss.     

FTIR spectroscopic study of the Cl- and Br-atom initiated oxidation of ethene

The reaction mechanism of the halogen (Cl and Br)-atom initiated oxidation of C₂H₄ was studied using the long path FTIR spectroscopic method in 700 torr of air at 296 ± 2 K. Among the major halogen-containing products were X? CH₂CHO, X? CH₂CH₂OH, and X? CH₂CH₂OOH (X = Cl or Br) which were shown to be formed via the self-reaction of the X? CH₂CH₂OO radicals, i.e., 2X? CH₂CH₂OO → 2X? CH₂CH₂O + O₂; (a) 2X? CH₂CH₂OO → X? CH₂CHO + X? CH₂CH₂OH + O₂ and (b) followed by X? CH₂CH₂O + O₂ → X? CH₂CHO + HO₂ and X? CH₂CH₂OO + HO₂ → X? CH₂CH₂OOH + O₂. From the observed yields of X? CH₂CHO and X? CH₂CH₂OH the branching ratios for reactions (a) and (b) were determined to be k_a/k_b = 1.35 ± 0.07(2σ) for both X = Cl and Br. In addition, the O₂-dependence of the rate constant for the Br + C₂H₄ reaction was determined by the relative rate technique as a function of O₂ partial pressure from 140 to 700 torr at 700 torr total pressure of N₂/O₂ diluent. Rate constants for the reactions of Cl-atoms with Cl-CH₂CHO and Br-atoms with Br-CH₂CHO were also determined to be [4.3 ± 0.2(2sigma;)] × 10^?11 and less than or equal to [1.83 ± 0.11(2σ)] × 10^?13 cm³ molecule^?1 s^?1, respectively.     

A New Method of Preparation of Ifosfamide and Cyclophosphamide; Synthesis of Side Products

Abstract

This study focusses on the preparation of ifosfamide (1; R¹=CH₂CH₂Cl, R²=NHCH₂CH₂Cl) and cyclophosphamide (2 R¹=H, R²=N(CH₂CH₂Cl)₂), standard drugs in tumor therapy, in order to avoid the alkylating educts like 2-chloroethylamine by introducing chlorine in the final reaction step. The reaction of the trimethylsilyl compounds (3; R¹=CH₂CH₂Cl, R²=NHCH₂CH₂0SiMe₃) and (4; R¹=H, R²=N(CH₂CH₂0SiMe₃)₂), respectively, with 2-chloro- 1,3,5-trimethyl-1,3,5-triaza-σ³λ₃-2-phosphoM-4,6-dione, followed by chlorination of the resulting product with sulphuryl chloride, furnished the cytotoxic drugs (1) and (2) [l].     

Fluordiazadiphosphetidine. 21. Mitt. Die Photochemische Chlorierung von 2,2,2,4,4,4-Hexafluoro-1,3-diethyl (und dipropyl)-1,3,2λ5,4λ5-diazadiphosphetidin und die Herstellung von 2,2,2,4,4,4-Hexafluoro-1-(cyanometyl)-3-methyl-1,3,2λ5,4λ5-diazadiphosphetidin

Summary The result of the chlorination of (CH₃CH₂NPF₃)₂ and (CH₃CH₂CH₂NPF₃)₂ with chlorine under UV-radiation were the new compounds CH₃CH₂(NPF₃)₂CH₂CH₂Cl and CH₃CH₂CH₂(NPF₃)₂CH₂CH₂CH₂Cl. The reaction of CH₃(NPF₃)₂CH₂Cl with KCN and crown-ether gave the new compound CH₃(NPF₃)₂CH₂CN.