Excited Π states of divinyl chalcogenides and chalcophenes

Electron transitions in divinyl chalcogenides (CH₂=CHXCH=CH₂, where X is S, Se, or Te) have been analyzed using UV absorption spectra of dialkyl and alkyl vinyl chalcogenides. The following relations for the orbital energies are found: ^* < ^* < ^* < ^* for Te and ^* < ^* < ^* < ^* for S and Se. For chalcophenes, a correlation between the energy of the excited state (E ^*) of specific symmetry, the ionization potential (I) and the electron affinity (EA) is obtained:E ^*=const+(I+EA)/2. The electron affinity of divinyl chalcogenides is estimated. The correlation between the excited ^* states of divinyl chalcogenides and chalcophenes is discussed.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 831–835, May, 1994.     

A semiempirical method based on geminal functions

An extention is reported of a previously proposed semiempirical approach based on geminal functions and formulas are given for the transition moments and the electronic population analysis.The case of pyridine is considered as an example and used to predict the n ^* or ^* character of its lower transition.This work was carried out with the financial support of the Consiglio Nazionale delle Ricerche (C.N.R.), Roma.     

The electronic spectrum of acrylonitrile

The vapor absorption spectrum of acrylonitrile CH₂CHCN has been measured in the vacuum ultraviolet region. In addition, an all-valence-electron molecular orbital calculation has been used to calculate the electronic structure and spectrum of the molecule. On the basis of the MO calculation, as well as a vibrational analysis of the observed spectrum, several electronic transitions are assigned. The lowest energy absorption band (2107Å, = 150) is assigned as an n ^* transition. Absorption bands at 2030Å (=1600), 1725Å ( = 2100), and 1570Å ( = 1920) are assigned as 0–0 bands associated with transitions that are, respectively, ^*,^*, and ^* in character.

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Zusammenfassung Das UV-Absorptionsspektrum von dampfförmigen Acrylnitril wurde gemessen und eine CNDO/2-Rechnung für die Elektronenstruktur durchgeführt. Auf dieser Basis konnten unter Zuhilfenahme der Analyse der Schwingungsstruktur im beobachteten Spektrum mehrere Banden zugeordnet werden: die 2107-Å-Bande ( = 150) einem n^*-Übergang, die drei Banden bei 2030Å ( = 1600), 1725Å ( = 2100) und 1570 Å ( = 1920)0-0-Übergängen von ^*-, ^*- bzw. ^*-Banden.

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Résumé Mesure du spectre d'absorption en phase vapeur de l'acrilonitrile CH₂CHCN dans la région de l'ultraviolet. Par ailleurs, la structure électronique et le spectre de la molécule ont été calculés à l'aide d'une méthode des orbitales moléculaires semi-empirique pour tous les électrons de valence. Sur cette base, ainsi que sur une analyse vibrationnelle du spectre expérimental, on procède à l'attribution de plusieurs transitions électroniques. La bande d'absorption de plus basse énergie (2107 Å, = 150) est attribuée à une transition n ^*. Les bandes d'absorption à 2030Å ( = 1600), 1275Å ( = 2100) et 1570Å ( = 1920) sont considérées comme des bandes 0 - 0 associées à des transitions ^*, ^* et ^* respectivement.

     

Mixed-Ligand Ruthenium(II) Complexes as Structural Units of Polynuclear Systems

Spectral and kinetic parameters were studied for phosphine-bipyridyl ruthenium(II) complexes, namely, cis-[Ru(Bipy)₂(PPh₃)X](BF₄), cis-[Ru(Bipy)(Dppe)X₂], and cis-[Ru(Bipy)(Dppene)X₂] (where Bipy is 2,2"-bipyridyl, PPh₃is triphenylphosphine, Dppe is 1,2-bis(diphenylphosphino)ethane, and Dppene iscis-1,2-bis(diphenylphosphino)ethylene; X = CN^–, NO₂ ^–), in the frozen (77 K) alcohol glasses (EtOH–MeOH, 4 : 1). The energies of the singlet and triplet metal-to-ligand charge transfer states d(Ru) *(Bipy) were found to increase in the order [Ru(Bipy)₂X₂] < [Ru(Bipy)₂(PPh₃)X]⁺< [Ru(Bipy)(Dppe)X₂] < [Ru(Bipy)(Dppene)X₂]. The luminescence quantum yields and the rate constants of the nonradiative deactivation of the lowest excited state ³MLCT increase in the same order.     

Calculation of some electronic excited states of formaldehyde

The optimized MO's of several excited states of formaldehyde have been calculated by means of a large basis set of modified Gaussian functions; particular attention has been paid to the * transition. The total energy of the various states has been obtained as the sum of the SCF and correlation energies; the last one has been calculated as a functional of the electronic density. The calculated values for the transition energies are in good agreement with the experiment. A strong interaction of the * state with the continuum is evidentiated; this fact can justify the absence of the * band in the absorption spectrum.     

Reactivity of pyrrole pigments,XXI: Structure and reactivity of Cu(II) and Zn(II) bilindione chelates

Summary Several Mn, Cu, and Zn chelates of etiobiliverdin-IV-, mesobiliverdin-IX, and its dimethyl ester are studied. The results show that the chemical constitution of the Cu biliverdin chelate corresponds to a formal metal oxidation state of (II) coordinated to a neutral radical of the NH trideprotonated biliverdin. The reactivity of the Cu(II) bilindione chelates in nucleophilic solvents agrees with that expected for a neutral radical structure of the ligand; in CH₃OH, they undergo oxidation towards dimethoxybilipurpurins. The magnetic behaviour of Cu(II) etiobiliverdinate-IV- in the solid state shows an intramolecular weak antiferromagnetic coupling d⁹Cu-to--radical (J=–23 cm^–1) and an intermolecular weak antiferromagnetic coupling -radical-to--radical (J=–45 cm^–1). The analogy of this magnetic behaviour to that of the cation radical of metalloporphyrins is discussed.

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Reaktivität von Pyrrolpigmenten, 21. Mitt.: Struktur und Reaktivität von Cu(II)- und Zn(II)-Chelaten von Bilindionen

Zusammenfassung Einige Mn, Cu and Zn Chelate von Etiobiliverdin-IV-, Mesobiliverdin-IX und seinem Dimethylester werden untersucht. Im Komplex koordiniert ein Metallatom (mit der Formalladung II) mit einem Neutralradikal des dreifach NH-deprotonierten Bilindions. Die Reaktivität des Komplexes gegenüber nukleophilen Lösungmitteln entspricht erwartungsgemäß dem eines neutralen -Radikals; in CH₃OH wird er zu Dimethoxybilipurpurin oxidiert. Bei Cu(II)-Etiobiliverdinat-IV beobachtet man im festen Zustand neben schwacher, antiferromagnetischer Kupplung zwischen d⁹Cu und -Radikal (J=–23 cm^–1) auch eine schwache, intermolekulare, antiferromagnetische Wechselwirkung zwischen zwei -Radikalen (J=–45 cm^–1). Dieses magnetische Verhalten wird dem des -Kationradikals von Metalloporphyrinen gegenübergestellt.

     

γ-Pyrone derivatives

3, 5-Dibromocomanic acid (3, 5-dibromo- -pyrone -2-carboxylic acid) VI and its ethyl ester, hitherto not described in the literature, are synthesized by the following route: diethyl acetonedioxalate (I) diethyl dibromochelidonate (III) (mono) ethyl dibromochelidonate (IV) diethyl 3, 5-dibromocomanate (V) VI. Direct bromination of diethyl bromochelidonate gives the ester III. 6-Bromocomenic acid and its ethyl ester are prepared, as well as 2-bromo-3-hydroxy - -pyrone. Bromocomanic acid (x-bromo--pyrone-2-carboxylic acid) XVI is synthesized by the following route: I (mono) ethyl chelidonate ethyl comanate comanic acid XVI. Oxonium salts are obtained: acid sulfates of comanic acid and ethyl comanate.For Part VII [1].     

Synthesis and chiral-optical properties of (+)-3-methyl-3,4-dihydroisoquinoline-1-thione

(+)-3-Methyl-3,4-dihydroisoquinoline-1-thione was obtained by sulfuration of (+)-3-methyl-3,4-dihydroisoquinolone with phosphorus pentasulfide or by cyclization of (+)--benzylethyl isothiocyante under the influence of polyphosphoric acid. Measurements of the rotatory dispersion and circular dichroism showed the presence of two positive Cotton effects due to n^* and ^* transitions in the thioamide chromophore, as well as Cotton effects apparently due to ^* transitions in the aromatic chromophore.Communication XXXV from the series Stereochemical Investigations. See [11] for communication XXXIV.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 94–97, January, 1976.     

Transformed steroids. 121. Synthesis of the δ-lactone of 3β-acetoxy-16α-hydroxy-6-oxo-24-nor-5α-chol-17(20)-en-23-oic acid

The synthesis of the ¹⁷⁽²⁰⁾-16 analog of natural chiogralactone is described. Attempts to introduce a 6-oxo group directly into the -lactone proved unsuccessful, since the first stage — saponification — took place with the formation of three products: the 3-hydroxy--lactone, the 3-hydroxy-²⁰⁽²²⁾-lactone, and the 15,17(20)-dienoic acid. The synthesis of the desired compound was effected from the ethyl ester of the 5,16-dienoic acid by the scheme 3-acetate3-tosylate6-hydroxy-3,5-cyclosteroid6-oxo-3,5-cyclosteroid6-oxo-5H--lactone. It has been shown that the cyclopropane ring in the 3,5-cyclosteroid -lactone is extremely stable under the conditions of acid treatments.N. D. Zelinskii Institute of Organic Chemistry, Academy of Sciences of the USSR, Moscow. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 184–187, March–April, 1981.     

Calculation of σ→π* and π→σ* transitions in vinylboranes

Calculations are presented of the energies of the ground and excited and electronic states of ethylene and substituted vinylboranes. The Pople-Segal-Santry method was employed throughout. It is concluded that the excited state of lowest energy in ethylene has * character whilst the lowest energy ultra-violet spectral bands of the latter compounds stem from ^* transitions.

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Zusammenfassung Valenzelektronenrechnungen nach Pople-Segal-Santry wurden für Äthylen und Vinylborane durchgeführt. Danach hat der niedrigste angeregte Zustand von Äthylen ^*-Charakter, während die längstwellige UV-Bande der Vinylborane einem ^* -Übergang entspricht.

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Résumé Calculs de l'énergie pour les états fondamentaux et excités et de l'éthylène et des vinylboranes substitués. Utilisation de la méthode de Pople-Ségal-Santry. L'état excité le plus bas pour l'éthylène résulte d'une transition ^* , alors qu'il résulte d'une transition ^* pour les vinylboranes.

     

Ab initio SCF and CI study of the electronic spectrum of pyridine N-oxide

Configuration interaction (CI) studies of ground, n *, * * electronically excited states are reported for pyridine N-oxide. The transition energy to the lowest * excited ¹ B ₂ state is calculated at 4.35 eV, compared to the experimental spectrum range of 3.67–4.0 eV. This state lies below the lowest n * excited ¹ A ₂ state calculated at 4.81 eV above the ground state. The only experimentally reported triplet state at 2.92 eV above the ground state is predicted to be the ³ A ₁ (*) state. The calculated energy lies at 3.27 eV. Numerous other high-lying singlet states as well as the triplet states have also been calculated. The intramolecular charge transfer character of the ground and the excited states have been studied in terms of the calculated dipole moment and other physical properties.     

Thermal and some other properties of the complexes crystallizing from the system Ni(II)-en-[Ni(CN)4]2−-H2O

Seven complex compounds exhibiting the compositions Ni(en)₃Ni(CN)₄·H₂O (I), Ni(en)₃Ni(CN)₄ (II),-Ni(en)₂Ni(CN)₄ (III), Ni(en)Ni(CN)₄·2H₂O (IV), Ni(en)Ni(CN)₄ (V), Ni(en)₂Ni(CN)₄ · 2.5H₂O (VI) and-Ni(en)₂Ni(CN)₄ (VII) were prepared from the system Ni-en-[Ni(CN)₄]^2–-H₂O. These compounds were examined by the methods of infrared spectroscopy, X-ray powder diffractometry, UV-VIS reflectance spectroscopy, and also by the measurement of magnetic moments. The thermal stability, the stoichiometry of thermal decomposition and the mutual transformations were investigated with a derivatograph. The reactions proceeding according to the following schemes were observed if the system was heated to appropriate temperature: (I)(II)(III)(V)(IV) and (VI)(VII)(III)(V)(IV) Process (VII)(III) represents isomerization. The reversibility of the process (V)(IV) is due to the high hygroscopicity of the anhydrous complex. The changes in structure in the course of the individual processes are discussed.

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Zusammenfassung Aus einem System Ni-en-[Ni(CN)₄]^2–-H₂O wurden sieben Komplexe der Formeln Ni(en)₃Ni(CN)₄·H₂O (I), Ni(en)₃Ni(CN)₄ (II),-Ni(en)₂Ni(CN)₄ (III), Ni(en)Ni(CN)₄·2H₂O (IV), Ni(en)Ni(CN)₄ (V), Ni(en)₂Ni(CN)₄ · 2.5H₂O (VI) und-Ni(en)₂Ni(CN)₄ (VII) hergestellt. Diese Verbindungen wurden mittels IR-Spektroskopie, Röntgenpulverdiffraktometrie, UV-Reflexionsspektroskopie und durch Messungen des magnetischen Momentes untersucht. Die Wärmestabilität, die Stöchiometrie des thermischen Zerfalles und die gegenseitigen Umwandlungen wurden mittels eines Derivatographen untersucht. Wird das System auf geeignete Temperaturen erhitzt, kann der Reaktionsverlauf durch folgendes Schema dargestellt werden: (I)(II)(III)(V)(IV) und (VI)(VII)(III)(V)(IV).Der Prozeß (VII)(III) verkörpert eine Isomerisierung. Die Umkehrbarkeit von Prozeß (V)(IV) ist auf die ausgeprägten Hygroskopieeigenschaften des wasserfreien Komplexes zurückzuführen. Es werden die im Ablaufe der einzelnen Prozesse vorgehenden Strukturveränderungen besprochen.

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Ni- -[No(N)]² -₂ Ni(en)₃Ni(CN)₄ · ₂ (I), Ni(en)₃Ni(CN)₄ (II),-Ni(en)₂Ni(CN)₄ (III), Ni(en)Ni(CN)₄-2H₂O (IV), Ni(en)Ni(CN)₄ (V), Ni(en)₂Ni(CN)₄ · 2,5H₂O (VI) -Ni(en)₂Ni(CN)₄ (VII). , , - , . , . (I)(II)(III)(V)(IV) (VI)(VII)(III)(V)(IV). (VII)(III) . (V)(IV) . .

     

A simplified View of δ → δ* Transition Energies in Compounds with multiple metal-metal bonds: The isolated δ — δ* manifold model

The energetics of the * transition in quadruply bonded complexes are investigated using a very simple valence-bond formalism, called the isolated * manifold (IDDM) model. In this model all electrons except for those that occupy the or * molecular orbitals are ignored, as are explicit metal-ligand interactions. The resulting equations allow the calculation of transition energies very inexpensively, albeit with poor quantitative agreement: the * transition in prototypical quadruple-bond systems is predicted to occur at energies greater than 70,000 cm¹. The model incorporates configuration interaction between the two¹ A _1g configurations (|| and |**|) to roughly the same extent as do correlated all-electron calculations. The application of the method to systems that involve relative changes in * transition energies, such as the torsional twisting of quadruple bonds, is more successful quantitatively.     

Electronic absorption spectra of 3-hydroxypyridine and 5-hydroxypyrimidine

The electronic absorption spectra ( ^* type) of the mixture of the enolic and zwitterionic forms of both 3-hydroxypyridine and 5-hydroxypyrimidine are interpreted by means of the Pariser-Parr-Pople type calculations.     

Electronic spectrum and thermal decomposition of nickel(II) complex with bis(N-γ-pyridyl-4-phenylbenzamide-hydrazone)

The unit cell parameters and the space group of the investigated compound were determined by means of X-ray diffraction.Analysis of the diffusion-reflection spectra of the crystalline powder and the absorption spectra of its alcoholic solutions permitted identification and quantitative characterization of the absorption bands of the crystalline complex of NiL₂(ClO₄)₂·3H₂O.Application of differential-thermal analysis allowed determination of the mechanism of thermal decomposition of the compound. From these measurements, the expected configuration of the basic molecule was verified, involving determination of the number of non-coordinated water molecules.

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Zusammenfassung Mittels Röntgendiffraktionsmethoden wurden Gitterzellenkonstanten sowie die Raumgruppe der untersuchten Verbindung bestimmt. Durch Analyse der erhaltenen Diffusions-Reflexionsspektren von kristallinem Pulver und des Absorptionsspektrums einer alkoholischen Lösung der Verbindung war es möglich, die Absorptionsbanden des Kristallkomplexes NiL₂(ClO₄)₂·3H₂O zu identifizieren und quantitativ zu charakterisieren. Anwendung von Differentialthermoanalyse ermöglicht die Bestimmung des Mechanismus der Zersetzungsreaktion der Verbindung. Durch diese Messungen, einschliesslich der Bestimmung der Anzahl nichtkoordinierter Wassermoleküle, wurde die erwartete Konfiguration des Grundmoleküles überprüft.

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NiL₂(ClO₄)₂·₂, L-N-- -4- . L-N---4- . , , . . , .

     

Heterogeneous reactions of solid nickel(II) complexes

The influence of different modes of preparation on the stoichiometry of thermal decomposition of isothiocyanatonickel(II) complexes with ammonia was studied. It was found that the complex Ni(NCS)₂(NH₃)₄ (I) prepared by heterogeneous reaction undergoes decomposition in two steps (–2 NH₃, –2 NH₃), while for complex II, of the same composition but prepared by homogeneous reaction from solution, the decomposition proceeds in three steps (–1 NH₃, –1 NH₃, –2NH₃). Electronic and infrared absorption spectra were used for the study of the spectral properties of the starting complex. It was found that the different stoichiometries of thermal decompositions of complexes I and II do not cause differences in the bonding strength of the ammonia molecules (chemical factor); this effect is rather brought about by physical factors such as different imperfections of the crystal lattice.

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Zusammenfassung Der Einfluß der Herstellung auf die Stöchiometrie der thermischen Zersetzung von Amin-Komplexen des Isothiocyanatonickels wurde studiert. Der Zerfall des Komplexes Ni(NCS)₂(NH₃)₄ (I), hergestellt durch heterogene Reaktion, verlief in zwei Etappen (–2 NH₃, –2 NH₃). Beim selben Komplex (II), hergestellt durch homogene Reaktion in Lösung, wurden jedoch drei Etappen beobachtet (–1 NH₃, –1 NH₃, –2 NH₃). Die Eigenschaften des Ausgangsproduktes wurden durch Elektronen- und IR-Spektroskopie untersucht. Das unterschiedliche thermische Verhalten ist nicht auf eine verschiedene Bindungsstärke der NH₃ Moleküle, sondern auf physikalische Ursachen, wie z. B. Unregelmässigkeiten im Kristallgitter zurückzuführen.

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Résumé On a étudié l'influence des diverses méthodes de préparation sur la stoechiométrie de la réaction de décomposition thermique des complexes de l'isothiocyanate de nickel(II) avec l'ammoniac. On a établi que le complexe Ni(SCN)₂(NH₃)₄, (I), préparé rar réaction hétérogène, subit une décomposition en deux étapes (–2NH₃, –2NH₃), tandis que le complexe (II), de même composition, mais préparé par réaction homogène, à partir de solutions, se décompose en trois étapes (–1NH₃,–1NH₃, –2NH₃). Les propriétés spectrales du complexe initial ont été étudiées par absorption électronique et infrarouge. On a trouvé que les différences de stoechiométrie des réactions de décomposition thermique des complexes (I) et (II) n'apportaient pas de différences entre les énergies de liaison des molécules d'ammoniac (facteur chimique). C'est plutôt à des facteurs physiques, comme les différentes imperfections du réseau cristallin, que cet effet serait dû.

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(II) . , Ni(NCS)₂(NH₃)₄ (I), , (–2NH₃,–2NH₃). , II , , (–1 NH₃,–1 NH₃ –2NH₃). . , I II ( ), , .

     

Two new triterpene glycosides from the holothurian Duasmodactyla kurilensis

Two new glycosides have been isolated from the total triterpene glycosides of the holothurianDuasmodactyla kurilensis: kurilosides A (III) and C (IV). It has been established that (III) is 16-acetoxy-3-{[O--D-glucopyranosyl-(1 4)-O--D-quinovopyranosyl-(1 2)]-[O-(3-O-methyl--D-glucopyranosyl)-(1 3)-O-(6-O-(sodium sulfato)--D-glucopyranosyl)-(1 4)]--D-xylopyranosyloxy}-4,4,14-trimethylpregen-9(11)-en-20-one, while the minor glycoside (IV) is 16-acetoxy-3-{O--D-quinovopyranosyl-(1 2)-[O-(3-O-methyl--D-glucopyranosyl-(1 3)-O-(6-O-(sodium sulfato)--D-glucopyranosyl)-(1 4)]--D-xylopyranosyloxy}-4,4,14-trimethylpregn-9(11)-en-20-one.Pacific Ocean Institute of Bioorganic Chemistry, Far Eastern Branch, Academy of Sciences of the USSR, Vladivostok. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 221–226, March–April, 1991.     

Synthesis and structure of (pyridine) bis(acetylacetonato) (1-methyl-1-phenylethylperoxo) cobalt (III)

Synthesis and structure of (pyridine) bis(acetylacetonato) (1-methyl-1-phenylethylperoxo) cobalt(III) complex are described.

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() () (III).

     

Calculations of electronic spectra of Fe and Co porphyrins and their anionic forms

Energies and intensities of electronic transitions of a number of Co and Fe porphyrins and their anionic forms have been calculated by the INDO/S-CI method in the Zerner parametrization. The results from the theoretical analysis are consistent with the basic relationships observed in the change of electronic spectra within the limits of isoelectronic series of compounds characterized by identical total number of -electrons and identical filling of the pair of d orbitals. It has been established that in the spectra of compounds of an isoelectronic series corresponding to the neutral state of the porphyrin ligand, the allowed electronic transitions are described by superpositions of two ^* configurations (la_1u 4e_g) ) and (3a ^2u 4e_g ) , two configurations of intermolecular charge transfer 3 (d 2b_1u) and (d 3b_2u), and two types of doubly excited configurations (la_1u, d 4e_g, 4e_g) and (3a _2u, d 4e_g, 4e_g). Data have been obtained on the energies and orbital nature of the even electronic states that are responsible for rapid exchange of excitation energy of the porphyrin molecules with the transition metals.Leningrad. Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 27, No. 2, pp. 144–151, March–April, 1991. Original article submitted September 28, 1989.     

Investigation of electronic structure of allenyl ethers by means of photoelectron and UV spectroscopy

A study of the photoelectron spectra of alkyl allenyl ethers has demonstrated their similarity to spectra of alkyl vinyl ethers, with the exception of a band in the 10.0–10.3 eV interval due to ionization of the -orbital of the allenyl fragment C=C. According to data obtained by photoelectron spectroscopy and MNDO quantum-chemical calculations, alkyl allenyl ethers with straightchain substituents exist primarily in the s-cis conformation. The stable conformation of allenyl tert-butyl ether is the s-trans form. The long-wave absorption bands in the UV spectra of alkyl allenyl ethers at 255–275 and 208–213 nm are assigned to electronic transitions of the ^* and ^{* *} types; these are quite insensitive to s-cis/s-trans isomerism.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 1, pp. 81–88, January, 1990.The authors are extremely grateful to V. K. Turchaninov for assistance in interpreting the spectra.