591-95-7Relevant academic research and scientific papers
Polylithiumorganic compounds. Part 28. The reaction of allene and alkyl substituted allenes with lithium metal
Maercker, Adalbert,Tatai, Andrea,Grebe, Burkhard,Girreser, Ulrich
, p. 1 - 8 (2007/10/03)
The reaction of allene (3a) and alkyl substituted allenes 1,2-hexadiene (3b), cyclopropylallene (3c), and vinylidene cyclopropane (3d) with lithium metal was investigated in order to access 2,3-dilithioalkenes 4a-d. These dilithioalkenes 4a-d are very reactive in polar solvents like THF and act as strong bases, either metalation of the starting allene 3a-d, the solvent, or sufficiently acidic intermediates like 8 a-d is observed. The metalation products 5-7 show follow-up reactions like 1,3-H shift to the corresponding 1-lithio-1-alkynes 8 and subsequent metalation to the dilithioalkynes 9. Additionally, lithium hydride elimination and ring-chain rearrangement (for 5c) are observed. 1,2-Hexadiene (3b) can be brought to reaction with lithium metal in the apolar solvent pentane, here the follow-up reactions are much slower due to the insolubility of 4b. In all cases the elucidation of the reaction pathways is hampered by the formation of complex mixtures of, amongst others, regio- and stereoisomeric products upon quenching with simple electrophiles.
Crossed-beam reaction of carbon atoms with hydrocarbon molecules. I. Chemical dynamics of the propargyl radical formation, C3H3 (X2B2), from reaction of C(3Pj) with ethylene, C2H4(X1/Ag)
Kaiser,Lee,Suits
, p. 8705 - 8720 (2007/10/03)
The reaction between ground-state carbon atoms, C(3Pj), and ethylene, C2H4(X1Ag), was studied at average collision energies of 17.1 and 38.3 kJmol-1 using the crossed molecular beams technique. Product angular distributions and time-of-flight spectra of m/e=39 were recorded. Forward-convolution fitting of the results yields a maximum energy release as well as angular distributions consistent with the formation of the propargyl radical in its X2B2 state. Reaction dynamics inferred from the experimental data indicate two microchannels, both initiated by attack of the carbon atom to the π-orbital of the ethylene molecule via a loose, reactant like transition state located at the centrifugal barrier. Following Cs symmetry on the ground state 3A″ surface, the initially formed triplet cyclopropylidene complex rotates in a plane roughly perpendicular to the total angular momentum vector around its C-axis, undergoes ring opening to triplet allene, and decomposes via hydrogen emission through a tight transition state to the propargyl radical. The initial and final orbital angular momenta L and L′ are weakly coupled and result in an isotropic center-of-mass angular distribution. A second microchannel arises from A-like rotations of the cyclopropylidene complex, followed by ring opening and H-atom elimination. In this case, a strong L-L′ correlation leads to a forward-scattered center-of-mass angular distribution. The explicit identification of C3H3 under single collision conditions represents a single, one-step mechanism to build up hydrocarbon radicals. Our findings strongly demand incorporation of distinct product isomers of carbon atom-neutral reactions in reaction networks simulating chemistry in combustion processes, the interstellar medium, as well as in outflows of carbon stars, and open the search for the hitherto unobserved interstellar propargyl radical.
Studies on the Thermal Conversion of Long-chain Alkynes at High Temperatures in the Gas Phase
Ondruschka, B.,Zimmermann, G.,Ziegler, U.,Kopinke, F.-D.,Teuber, M.
, p. 273 - 284 (2007/10/02)
In the gas phase pyrolysis of long-chain alkynes C5 to C9 at 773 to 873 K, a remarkable portion of molecular reaction (retro-ene analogous decompositions as well as cycloisomerizations of the parent alkynes to cyclopentenes alkylated in 3-position) takes place besides the thermal conversion of the starting compounds via radical chain processes.The different products were separated by GC and the main products identified by means of different methods.The mechanisms of formation of the major products are discussed.
Radical-Chain Addition of Benzenethiol to Allenes. Analysis of Steric Effects and Reversibility
Pasto, Daniel J.,Warren, Steven E.,Morrison, Marjorie A.
, p. 2837 - 2841 (2007/10/02)
The radical-chain addition of benzenethiol to the monoalkylallenes 1a-e and the 1,1-dialkylallenes 6 and 8 has been studied.Attack by the benzenethiyl radical occurs at C2 and C3 of 1b-e in a ratio of 83:17.Increased attack (25percent) at C3 occurs with tert-butylallene (1a).The 1,1-dialkylallenes undergo attack only at C2.Deuterium-labeling studies indicate that the thiyl radical addition step is not detectably reversible under the reaction conditions.The internal alkene adducts 2, 3, 9 and 10 are the kinetically favored products.Rapid and reversible addition of the thiyl radical to the adducts results in complete stereochemical equilibration during the course of the reaction.The hydrogen atom abstraction step is reversible under the reaction conditions with 1a and 8 but not with 6 or the other monoalkylallenes.Treatment of the adducts derived from 1a and 8 with a catalytic quantity of iodine results in isomerization to the more thermodynamically stable adducts 4 and 11.The kinetics and thermodynamics of these reactions are discussed, and steric strain energies for the CH3...SC6H5 and t-Bu...SC6H5 interactions have been estimated to be 0.8-0.9 and 3.9-4.0 kcal/mol, respectively.
