Radical Telomerization Of Propylene Research Articles

Stereodirectivity in the radical telomerization of propylene with CCl4, initiated by metal carbonyl systems

1. 13C NMR and capillary GLC have been used to show that in the telomerization of propylene with CCl4, initiated by TBP, Cr(CO)6, Fe(CO)5+DMF, or W(CO)6+PPh3, the racemic diastereoisomeric forms of the telomers CCl3[CH2CH(CH3)]n Cl (n=2,3) are formed in approximately equal amounts. 2. The similarity in the stereodirectivity of the telomerization, whether initiated by TBP or by Cr(CO)6, Fe(CO)5+DMF, or W(CO)6+PPh3, indicates that in the last three cases the reaction proceeds by a stepwise free-radical mechanism.

Chromatographic-mass spectrometric study of the products of radical telomerization of propylene with CCl4

1. In the radical telomerization of propylene with CCl4, isomeric telomers with abnormal insertion of the monomeric units are formed in small quantities together with telomers with a normal structure. 2. The relative concentration of the abnormal telomers increases with an increase in the length of the chain of the telomer.

Investigation of the stereochemistry of the radical telomerization of propylene by polyhalomethanes by the method of conformational PMR analysis

1. The stereochemical radical telomerization of propylene with CCl4 and CBrCl3 was investigated by the method of conformational PMR analysis at 60°. The relative configurations of diastereomeric racemic forms of the telomer CCl3CH2CH(CH3)CH2CHBrCH3 were established according to conformational data, considering the previous independent assignments for CCl3CH2CH(CH3)CH2CHCICH3 and structurally close chiral polychloroalkanes. 2. The reactions of chain transfer to CCl4 and CBrCl3 forα, γ-disubstituted aliphatic radicals have the same stereodirection. The approach of the telogen to the radical from the side opposite to the position of the substituent in the next-to-last monomer unit proved to be the preferential direction of attack. 3. Differences in the parameters of the PMR spectra of diastereomeric forms of nonsymmetrical polyhalosubstituted aliphatic hydrocarbons with two chiral centers from the similar dissymmetrical compounds retaining certain elements of symmetry, important for the assignment of the configurations, were detected.

Investigation of the stereochemistry of the radical telomerization of propylene with 1,1,1,3-tetrachlorobutane by the method of conformational PMR analysis

1. The stereochemistry of the radical telomerization of propylene by 1,1,1,3-tetrachlorobutane, catalyzed by Fe(CO)5 with additions of i-C3H7OH or dimethylformamide at 95°, was investigated by the method of conformational PME analysis. 2. To evaluate the diastereomeric composition of the lower member of the telomer homolog series of 2,4,4,6-tetrachloroheptane, we studied the distribution of the rotational isomers of the molecule in several solvents of different types and assigned the configurations of two racemic forms, on the basis of a comparison of the conformational composition and differences in shielding constants of the methylene protons. 3. A total lack of stereodirection of the substitution reaction with the participation of the intermediate acyclic radical, probably determined by the absence of induction of the asymmetrical atom at a 1,5-distance from the reaction center, was detected.

Influence of certain iron compounds on the distribution of telomer homologs and the particular chain transfer constants in the radical telomerization of propylene with CCl4

1. The radical telomerization of propylene with CCl4 was studied in the presence ofπ-allylirontricarbonyl chloride,π-allylirontricarbonyl iodide (at 105°), FeCl3 (145, 200°), and iron triacetylacetonate (105, 145°). 2. The compounds mentioned induced a multiple increase in the yield of the adduct, rate of telomerization, and constants of chain transfer of the radicals CCl3[CH2CH(CH3)]n. with n=1 and 2 within a definite range of concentrations. The apparent rate of transfer of chlorine forπ-C3H5Fe(CO)3Cl and FeCl3 passes through a maximum in a rather narrow region of initial concentrations of the iron compounds, followed by a sharp decrease to some constant value. Raising the temperature lowers the transmitting activity of FeCl3. 3. To explain the observed effects, a hypothesis was advanced on the possibility of direct interaction according to the mechanism of transfer of the ligand of the intermediate or initial chlorine-containing iron compound with telomer radicals. Some general principles of the initiation of radical telomerization of C3H6 with CCl4 by iron compounds are discussed.

Structure of products and stereodirection of the radical telomerization of propylene with chloroform

1. Four types of telomer homologs, corresponding to cleavage of the C-H and C-Cl bonds in the telogen during chain transfer and the formation of the radicals ĊCl3- and ĊHCl2-, carrying the kinetic chain, were identified in the products of radical telomerization of propylene with CHCl3 by the methods of gas-liquid chromatography, mass, IR, NQR, and PMR spectroscopy. 2. The addition of the radicals CCl3[CH2CH(ĊH3)]n with n≥2to propylene proceeds with some stereoregularity and obeys close stereochemical principles with chain transfer by these radicals to CCl4.

The particular chain transfer constants in the radical telomerization of propylene with CCl4, initiated by iron pentacarbonyl

1. The radical telomerization of propylene with CCl4 was studied in the presence of various amounts of Fe(CO)5 at 105, 145, and 200° without additions of nucleophilic solvents. It was established that iron pentacarbonyl in the system C3H6-Fe(CO)5-CCl4 is not only an initiator, but participates extremely actively in the development of the kinetic chain when definite concentrations are reached, many times increasing the yield of the adduct and the first constant of transfer. As the temperature is increased, the initiating activity of Fe(CO)5 increases, but its influence on the yield of the adduct decreases sharply. 2. It was hypothesized that the action of Fe(CO)5 is associated with the formation of an intermediate complex, containing coordinated chlorine and capable of entering together with the telogen into a reaction with the CCl3CH2CHCH3 radical (according to the mechanism of ligand transfer); some kinetic principles confirming this hypothesis are discussed.

Influence of pressure on the particular transfer constants and stereodirectedness of radical telomerization of ethylene and propylene with carbon tetrachloride and chloroform

1. The particular constants of chain transfer in the telomerization of ethylene with CCl4 and CHCl3 and propylene with CCl4 at 95° and a pressure of 150–180 or 2400 kg/cm2 were determined. The change in the rate of reactions of substitution with cleavage of a C-H bond with increasing pressure (and the volume effects of activation) is substantially lower than for substitution of the C-Cl bond with the participation of the same trichloroalkyl radicals. 2. Increasing the pressure increases the probability of the formation of the racemic iso-modification of 1,1,1,1-tetrachloro-3,5-dimethyloctane in the radical telomerization of propylene with CCl4. The reaction of addition or substitution of CCl3[CH2CH(CH3)]n radicals with conservation of the configuration of the preceding unit proceeds through transition states with a somewhat smaller volume than for processes with syndiotactic chain propagation.

Stereodirection of the radical telomerization of propylene by carbon tetrachloride

1. The influence of temperature (55–200°) on the distribution of racemic diastereomeric i-, s-, and h-modifications of 1, 1, 1, 7-tetrachloro-3, 5-dimethyloctane in the radical telomerization of propylene with CCl4 was studied in a broad range of reagent concentrations. 2. Using statistical methods of evaluating the relative content of i-, s-, and h-forms, the possibility of stereodirected chain transfer and addition at the double bond of CCl3[CH2CH(CH3)]n radicals was demonstrated (chiefly the syndio-direction, although the yield of the i-form almost doubles from 55 to 200°); the stereochemical nature of the substitution with the participation of aliphatic radicals was studied for the first time. 3. A hypothesis was advanced on the stereoregulating influence of the substituent in the penultimate unit of the growing telomer radical (1, 3-asymmetrical induction).

Structure of the products of radical telomerization of propylene by carbon tetrachloride

Isomeric telomerization products of C3H6 with CCl4 with n=3 were isolated, and it was shown by the methods of mass, IR, NQR, and PMR spectroscopy that these isomers are racemates of the two possible diastereoisomers of 1,1,1,7-tetrachloro-3,5-dimethyloctane.