Sidney I. Miller

Substituted Methanes. X. Infrared Spectral Data, Assignments, Potential Constants, and Calculated Thermodynamic Properties for CF3Br and CF3I

Infrared wave numbers, relative intensities, and percent transmission curves have been obtained for CF3Br and CF3I in the region 400–2200 cm−1. Assignments are given for the observed bands, in which the assignments of Plyler and Acquista for ν2 and ν3 are interchanged. Potential constants were calculated for both molecules by the Wilson FG matrix method. And, finally, the heat content, free energy, entropy, and heat capacity for the ideal gaseous state at 1 atmos pressure were calculated for 12 temperatures from 100°to 1000°K, using a rigid rotator, harmonic oscillator approximation.

Syntheses with diacetylenic ketones: 5-Membered rings by anti-michael addition

Abstract Syntheses with diphenylethynylketone and di-n-hexynylketone lead to a variety of products deriving from attack at the ketone and/or one or both triple bonds. Adducts with amines, hydrazines, mercaptans, active methylene compounds, and tetraphenylcyclopentadienone were obtained. Among the 6-membered cyclic products, pyridones, and pyrones are expected, while deca-substituted benzophenones are unusual. A novel route to 5-membered rings, e.g. oxo-Δ 2 -pyrrolines, thiacyclopentenones (and 3-hydroxythiophenes), and cyclopentenones makes the diethynylketones useful intermediates.

Stereoselection in the Elementary steps of Organic Reactions

Publisher Summary This chapter describes a number of principles or causes of stereoselection associated with bonding, steric, thermodynamic, electrical, and mechanical factors, inherent in the stereoprocess. It deals with the relation between the properties of intermediates, such as carbanion or syn-anti isomers, rate and equilibrium conditions and stereoselectivity are also discussed. The chapter also examines representative systems and reactions to see the relevance of the principles of stereoselection. The focus is on the stereo-process that include two axioms—every reaction at the molecular level is stereospecific (axiom 1) and for a collection of molecules the elementary reaction is stereoselective (axiom 2). The shape of simple species is examined. Both valence bond (VB) and molecular orbital (MO) theories are used to explain the observed shapes of molecules. The preferred shapes of the simple species are known or can be guessed from the numbers and kinds of bonding and nonbonding electron pairs. Several valence bond results and molecular orbital results are discussed.

Syntheses and properties of H-1,2,3-triazoles☆

About twenty new H-1,2,3-triazoles (T) were readily synthesized by nucleophilic attack of sodium azide on activated acetylenes in dimethylformamide. Typical activating groups were COR, COOR, O2NC6H4 PO(OC2H5, COT, and (C6H5)3P+. Propynyl 4-triazolyl ketone or phenylethynyl 4-triazolyl ketone may be converted to acylic adducts (triazolylketoenamines), biheteroaromatic systems (isoxazolytriazoles, pyrazolytriazoles), as well as to ditriazolyl ketones. Certain T properties were examined in detail. The apparent pK′s for our group of ca 30 triazoles were in the range 4·95−9·45 in ethanol-water (v/v 1/1) at 25°. The Hammett correlation for five 4-aryl-T was log Ka = 0·89σ− −9·21 and for seven 4-aryl-5-carbethoxy-T was log Ka = 1·45σ−6·95. The UV spectra of T are similar to those of other heteroaromatic and phenyl compounds: interesting analogies between triazolyl and phenyl, e.g., ”ortho“ crowding effects, appear to be indicated in the spectra of compounds related to biphenyl, stilhene and benzophenone. With regard to structure assignment on the basis of spectra, characteristic features of UV and IR spectra of the H-1,2,3-triazoles are discussed.

Stereoselection in nucleophilic substitution at an sp2 carbon

Abstract The stereochemical possibilities of the title reaction are considered in detail, taking into account both the relative rates of rotation, inversion, formation and decomposition, and the stabilities of the species involved. Briefly, a rationale for predominant retention is outlined and a set of conditions favorable to inversion are described. First it is assumed that the exchange of X and Y in eqn (1) includes the anion 1 or 2 as an intermediate. The reaction pathways can be mapped in the form of graphs: mechanisms by selected routes can now be related to the characteristics of the system or modified to accommodate special mechanistic alternatives, e.g. addition-elimination and concerted substitution. In the graph dealing with the pyramidal anion BAC-CXYW, the favored retention route is anti formation and syn decomposition, while the inversion route is syn formation and syn decomposition.These stereospecific models arise for different reasons: in the first, certain rotomers of 1 are favored because of the trans (contra-gauche) effect; in the second, strong ion pairing predominates over other factors. This scheme has to be altered for the “pyramidal” anion derived from the Σ isomer of AN=CXW, since the anti-syn sequence may give both retention and inversion. In the graph dealing with the trigonal anion BAC-CXYW or AN-CXYW, retention paths are always favored. All of the stereospecific paths described hold for specified models—when constraints are removed, stereoconvergence follows.

Vibrational Spectra, Potential Constants, and Calculated Thermodynamic Properties of cis‐ and trans‐BrHC=CHBr, and cis‐ and trans‐BrDC=CDBr

Raman displacements for the liquid and infrared absorption wave numbers for both liquid and gas, together with quantitative depolarization factors for the Raman lines and semiquantitative relative intensities for both Raman and infrared bands, have been obtained for cis‐ and trans‐BrHC=CHBr and cis‐ and trans‐BrDC=CDBr. Assignments, consistent with the selection rules, were made for the 4 molecules. As a further check on the assignments a normal coordinate treatment (Wilson FG matrix method) was carried out. The heat content, free energy, entropy, and heat capacity for each of the molecules were calculated for 12 temperatures from 100 to 1000°K for the ideal gaseous state at 1 atmos pressure. Finally the energy difference between the cis‐ and trans‐isomers of C2H2Br2 has been calculated.

Synthesis and spectral properties of 1,4- and 1,3-pentadiynes

Abstract “Skipped” (1,4-) diynes have been prepared by coupling alkynyl Grignard reagents with propargyl bromides. Treatment with base isomerizes the 1,4- to conjugated 1,3-diynes. Two alleged routes to 1,5-diphenyl-1,4-pentadiyne have now been shown to give 1,4-diphenylbutadiyne. Spectral properties, NMR, IR, UV, are given for both series. Shoolerys rule is found useful in predicting the chemical shift, τ(CH2),for these and other kinds of acetylenic compounds. On the basis of their UV spectra, one can say that in the 1,4-diynes there is little, if any, conjugation “through” the internal methylene group, and what conjugation there is, is less than that in 1,3-diynes.

Nucleophilic substitution at an acetylenic carbon

Phenylhaloacetylenes are triphilic towards methoxide ion in methanol. With phenylchloroacetylene (1′), methoxide attacks ∼0·2% on chlorine, ∼99% on carbon 1, and ∼1% on carbon 2; with phenylbromoacetylene (1), methoxide attacks ∼5% on bromine, ∼83% on carbon 1, and ∼11% on carbon 2. The first detectable products, phenylacetylene, phenylmethoxyacetylene (2), (E)-β-bromo-β-methoxy- styrene, and (Z)-β-bromo-α-methoxystyrene lie on discrete mechanistic paths and are not interconvertible under the reaction conditions. Comparable amounts of alkynyl and alkenyl ethers are formed by attack on carbon 1. The element effects for attack on halogen, K(Cl)/k(Br) ⋍ 0·4, and on carbon 1, k(Cl)/L(Br) ⋍ 1·6 are consistent with the notion of independent competing processes. Phenylmethoxyacetylene is a short- lived transient; its formation and decay (with methoxide) rate constants at 78° arc k1′2 (Cl) 0·6 × 10−4 * or k12 (Br) 0·5 × 10−4 and Kj 1·7 × 10−3 M−1 sec−1. Previously, the intermediacy of alkoxyacetylenes under analogous conditions has only been surmised. In the course of this work, five of the six bromomethoxystyrenes were prepared and some of their distinctive chemistries, as well as those of the corresponding carbonyl compounds, were worked out (eq 2–4).

Selectivities in 1,2,3-triazolide displacements of halides and additions to alkynes

Abstract 4,5-Dicarbomethoxy-1,2,3-triazolide or 4-phenyl-1,2,3-triazolide displace chloride from ethyl chloroacetate or β-chloropropionate to give both 1-N and 2-N alkylated products. Our highest 2-N to 1-N selectivity was ca 5/1 and was found with the base triethylamine in DMF. The same triazolides and others add to alkynes, e.g. ethyl propiolate, methyl acetylenedicarboxylate, phenylpropiolaldehyde, ethyl phenylpropiolate, etc, to give Michael adducts at the 2-N position exclusively. Here the usual preference holds, i.e., the anti adduct is favored, but anti to syn isomerization usually sets in. On the basis of the available data for nucleophilic substitutions and additions, a limited directioselectivity pattern emerges for H-1,2,3-triazoles ( T ) and their anions ( T − ): neutral T almost invariably leads with 1-N; T t- - usually adds to unsaturates at 2-N; unsubstituted, 4-substituted and 4,5-disubstituted T − attack organic halides at both 1-N and 2-N. Compared to phenyl, 2-triazolyl exerts a greater deshielding effect on proton chemical shifts; these and other patterns in the PMR spectra of the Michael adducts are discussed. CNDO calculations indicate that the 1-H is more stable than the 2-H-1,2,3-triazole and that in both neutral triazole and in triazolide, the 1-nitrogen position should lead nucleophilic attacks-this directioselectivity prediction is only partly (and probably fortuitously) correct.

Skipped diynes—VI : Triethynylcarbinols, related diynes and allene dimers

Abstract The tris (t-butylethynyl)carbonium ion (δ CH 3 1·86) has been prepared in chlorosulfonic acid from the corresponding carbinol. Apart from a few esters, triethynylmethyl derivatives appear to be unknown, contary to previous claims. Tris (t-butylethynyl) carbinol ( 1a ) may, however, be converted into 1,1-di-t-butylethynyl-3-t-butylallenes, e.g., chloride, bromide, and carboxylic acid. These haloallenes dimerize ( ∼ 25°) to give one of the fourteen possible structures, the unsymmetrical 1,2-dimethylenecyclobutane ( Z - I ). Tris (1-propynyl) carbinol is generally similar to 1a , although its chloroallene leads directly to two dimers (Eq 4). Upon heating ( ∼ 100°) dimer Z - 1 (Cl) is quantitatively isomerized to the trans - II (Cl) dimer. Thus far, the known chemistry of I and II is largely associated with replacement of the halogen by acetate, alkoxide and hydroxide.