Non-aromatic Ring Research Articles

Conformation of non-aromatic ring compounds, part 57 : Dipole moments of cis- and trans-2-alkoxy-4-methyltetrahydropyrans

Conformation of non-aromatic ring compounds, part 57 : Dipole moments of cis- and trans-2-alkoxy-4-methyltetrahydropyrans

The conformation of non-aromatic ring compounds. XLVI. The crystal and molecular structure of 2,2'-dichlorotrimethylene sulphite

The conformation of non-aromatic ring compounds. XLVI. The crystal and molecular structure of 2,2'-dichlorotrimethylene sulphite

The conformation of non-aromatic ring compounds—XL: Characteristic vibration frequencies of some cyclic vicinal dihalogenides with anti configuration—I.

A study of the infrared and Raman spectra of vicinal dihalogenides with anti (diaxial) orientation in the cyclohexane, -pentane, dioxane, tetrahydropyran and steroid series reveals that the two CHal stretching frequencies occur characteristically as a strongly coupled pair: an intense Raman band (ν s) and a strong infrared active mode of vibration at lower frequency (ν as). The position of the bands and the difference ν s-ν as are functions of the structure in the vicinity of the CHal bond, the CCl stretching frequencies being sensitive to structural variations more than the CBr frequencies. In mixed dihalides (bromo-chlorides) the stretching modes are also strongly coupled. Frequency ranges of sec—sec and sec—tert dihalides are given. The CHal stretching frequencies of the diequatorial conformations are weakly coupled. It is shown that a relatively small set of empirically determined values suffices to predict with fair accuracy the frequencies, or, in coupled systems, the average frequency, displayed by vic dichlorides and dibromides.

The conformation of non-aromatic ring compounds, part XLIX relationship between the conformational equilibria in halogenated open-chain and six-membered carbocyclic compounds

The conformation of non-aromatic ring compounds, part XLIX relationship between the conformational equilibria in halogenated open-chain and six-membered carbocyclic compounds

Conformation of non-aromatic ring compounds, Part L boat/twist-boat pseudorotation in six-membered ring compounds

Conformation of non-aromatic ring compounds, Part L boat/twist-boat pseudorotation in six-membered ring compounds

The conformation of non-aromatic ring compounds—XLIII

Abstract The IR and Raman spectra of 3-halogeno- and trans-3,4-dihalogenotetrahydrofurans were recorded. The conformations with the halogen atoms in axial position were found to predominate in solution, the substituents occupying the most puckered part of the ring. For the 3-halogeno compounds, this conclusion is confirmed by the dipole moments.

Conformation of non-aromatic ring Compounds—XXV: Geometry and conformation of ring D in some steroids from X-ray structure determinations

A quantitative description of (solid state) steroid ring D puckering and conformation in terms of maximum angle of torsion ϕ m and “phase angle” of pseudoration Δ has considerably improved the approach to the problem of describing flexible 5-membered rings. The maximal torsional parameter ϕ m of all steroid rings D is relatively constant (47°) although a slight tendency to increase with increasing phase angle is noted. The phase angles of 17-keto steroids are negative (= rotation toward C(14) envelope form), those of the otherwise substituted steroids are limited to a rather narrow range comprising about one quarter of the possible circuit. A C(13) envelope has not been found thus far. Some empirical rules that may serve as a basis for the discussion of ring D conformation can now be recognized. In first approximation the nature of the C(17) or C(16) β substituent (except keto) has no discernible influence. Extreme deformations of rings A, B and/or C do affect ring D. The effect of the angular methyl groups C(18) and C(19) cannot yet be assessed for lack of information on nor-steroids. X-ray studies on a diversity of well chosen compounds will be necessary to elucidate the role of each conformation-determining factor. Solution data (NMR, infrared, ORD, CD, and dipole moments), interpreted in accordance with the now established “conformation laws” of ring D, may be of considerable help in this respect.

Conformation of non-aromatic ring compounds—XLIV : NMR spectra and dipole moments of some 2-substituted 1,3-dioxolanes

Proton spin coupling constants and chemical shifts (AA′BB′ part) in a number of 2-substituted 1,3-dioxolanes of the types: ▪ Combination of NMR and dipole amount data indicates rotation about the C2OR bond giving rise to an equilibrium between anti and gauche forms; the equilibrium constant depends on the bulk of group R. The mean phase angle of pseudorotation shifts slightly towards that of an envelope form, i.e. towards a smaller torsional angle of the CH 2CH 2 fragment, on passing from anti to gauche. From earlier X-ray data on bis-1,3-dioxolane 13 it is deduced that the maximum possible value of ϕ in 1,3-dioxolanes is about 30°; the actual value in the solid is 21°.

Conformation of non-aromatic ring compounds—XXIV : On the geometry of the perhydrophenanthrene skeleton in some steroids

A quantitative description of the conformation of the A,B,C,-moiety of eight steroids in terms of valency and torsional angles is given. The geometrical details of the molecules from X-ray structure determinations are compared with those obtained from theoretical considerations on appropriately substituted cyclohexane and cyclohexene rings. It is shown that the use of such building material leads to a qualitative agreement. A number of interactions present in a steroid, but not in a cyclohexane unit, prevents a quantitative agreement. The steroid skeleton (all trans) has a somewhat bent overall shape. The occurrence of conformational transmission effects is discussed and a number of rules concerning the torsional angles around junctions given.

The conformation of non‐aromatic ring compounds. Part 37: The Crystal Structure of 2‐Oxo‐2‐phenoxy‐1,3,2‐dioxaphosphorinane

Abstract2‐Oxo‐2‐phenoxy‐1, 3, 2‐dioxaphosphorinane (propane‐1, 3‐phenylphosphate) crystallizes in the orthorhombic system, space group Pna21, Z = 4. The unit cell dimensions are a = 15.55, b = 11.06, c = 5.97 Å. The structure was solved by the heavy atom technique and refined by the method of least squares using eye‐estimated three‐dimensional data obtained with copper radiation at room temperature. The dioxaphosphorinane ring has the chair conformation with the double‐bonded oxygen in equatorial and the phenoxy group in axial position.

The conformation of non-aromatic ring compounds. XXI. The crystal and molecular structure of 2-phenyl-1,3-dithiane

The conformation of non-aromatic ring compounds. XXI. The crystal and molecular structure of 2-phenyl-1,3-dithiane

The conformation of non-aromatic ring compounds. XVI. The crystal structure of 2β,3α-dichloro-5α-cholestane (modification β) at –120°C

The conformation of non-aromatic ring compounds. XVI. The crystal structure of 2β,3α-dichloro-5α-cholestane (modification β) at –120°C

The conformation of non-aromatic ring compounds. XVII. The crystal structures of 2α,3β-dichloro- and 2α,3β-dibromo-5α-cholestane

The conformation of non-aromatic ring compounds. XVII. The crystal structures of 2α,3β-dichloro- and 2α,3β-dibromo-5α-cholestane

Investigations into the conformation of non-aromatic ring compounds—XI : Coupling constants in some cis-2,3-disubstituted-1,4-dioxans: a reassignment of the structure of trans-naphthodioxan

Vicinal coupling constants (AA′BB′ part) in cis-2,3-dichloro-1,4-dioxan (I, m.p. 54°) in cis-2,3-diphenyl-1,4-dioxan (II, m.p. 132°) and in so-called trans-1,4,5,8-naphtho-dioxan (III, m.p. 136°) are reported. The coupling constants of III provide unambiguous evidence that the structure of III is actually cis. The couplings of I, II and III clarify previous conflicting views and show that these compounds are rapidly inverting (ea) chair forms of closely similar geometry. The couplings in cis-2,5-diphenyl-1,4-dioxan (VII, m.p. 121°) support the previously assigned structure.

The conformation of non-aromatic ring compounds. XIV. The crystal structure of trans-2,3-dichloro-1,4-dithiane at –180°C

The conformation of non-aromatic ring compounds. XIV. The crystal structure of <i>trans</i>-2,3-dichloro-1,4-dithiane at –180°C

Investigations of the conformation of non-aromatic ring compounds. XIII. The crystal structure of cyclohexane-1,3-dione at –140°C

Investigations of the conformation of non-aromatic ring compounds. XIII. The crystal structure of cyclohexane-1,3-dione at –140°C

The conformation of non-aromatic ring compounds. VII. Crystal structure oftrans-2,5-dichloro-1,4-dioxane at 125°C

The conformation of non-aromatic ring compounds. VII. Crystal structure of<i>trans</i>-2,5-dichloro-1,4-dioxane at 125°C

Investigations into the conformation of non-aromatic ring compounds XII. Cyclohexanedione 1,4 and related compounds.

Investigations into the conformation of non-aromatic ring compounds XII. Cyclohexanedione 1,4 and related compounds.

Investigations into the conformations of non-aromatic ring : Compounds V. The nmr spectra of dihalogenocyclohexannes

Investigations into the conformations of non-aromatic ring : Compounds V. The nmr spectra of dihalogenocyclohexannes