THE ELECTRONIC SPECTRA OF SOME ANIONIC POLYMERIZATION SYSTEMS

1964 ◽  
Vol 42 (6) ◽  
pp. 1255-1260 ◽  
Author(s):  
S. Bywater ◽  
A. F. Johnson ◽  
D. J. Worsfold
Keyword(s):  
Alkali Metal ◽  
Absorption Spectra ◽  
Anionic Polymerization ◽  
Electronic Spectra ◽  
Alkali Metals ◽  
Ultraviolet Absorption ◽  
Tetrahydrofuran Solution ◽  
Sodium And Potassium

The ultraviolet absorption spectra of living anionic polymerizing systems have been measured with sytrene, butadiene, and isoprene as the monomers; with lithium, sodium, and potassium as the alkali metals; and with tetrahydrofuran, cyclohexane, and benzene as the solvents. For any monomer the similarity of the spectra obtained with the various metals and solvents leads to the conclusion that the alkali metal – carbon band has the same structure under the various conditions. From other evidence the bond is considered to be ionic in all cases. The diene monomer anions in tetrahydrofuran solution were found to undergo a series of isomerizations, some of them comparable in speed to the consumption of monomer.

LIGHT ABSORPTION STUDIES: PART XII. ULTRAVIOLET ABSORPTION SPECTRA OF BENZALDEHYDES

1958 ◽  
Vol 36 (10) ◽  
pp. 1362-1370 ◽  
Author(s):  
J. C. Dearden ◽  
W. F. Forbes
Keyword(s):  
Absorption Spectra ◽  
Light Absorption ◽  
Electronic Spectra ◽  
Spectral Properties ◽  
Ultraviolet Absorption ◽  
Benzene Derivatives ◽  
Formyl Group ◽  
Steric Interactions ◽  
Absorption Studies ◽  
Acetyl Group

The electronic spectra of benzaldehydes in the region 220–360 mμ are recorded and discussed in terms of previously stated hypotheses. The formyl group is shown to endow benzene derivatives with spectral properties similar to those of the acetyl group in acetophenones, except that steric interactions are slightly modified.

scholarly journals The absorption spectra of mixed metallic vapours.—II. The spectra of volatile compounds of magnesium and the alkali metals

1925 ◽  
Vol 109 (749) ◽  
pp. 194-197 ◽  
Keyword(s):  
Absorption Spectrum ◽  
Fine Structure ◽  
Volatile Compounds ◽  
Absorption Spectra ◽  
Volatile Compound ◽  
Alkali Metals ◽  
Band System ◽  
Early Description ◽  
Band Spectra ◽  
Sodium And Potassium

In a previous communication (‘ Roy. Soc. Proc.,’ A, vol. 105, p. 221 (1924) a band system has been described which is found only in the absorption spectrum of the mixed vapours of sodium and potassium. It was suggested in explanation of this observation that molecules of a volatile compound of the two metals must be present in such mixtures; a supposition which H. G. Smith has since confirmed by comparison of the fine structure of these bands with that of the normal sodium and potassium band spectra (‘ Roy. Soc. Proc.,’ A, vol. 106, p. 400 (1924) ). Bands probably analogous in origin have now been found in the absorption spectra of mixtures of the vapours of magnesium and alkali metals. Two of these spectra —which may be called the “magnesium-sodium” and the “magnesium-potassium” bands —were recorded many years ago by Liveing and Dewar (‘ Roy. Soc. Proc.,’ vol. 27, p. 350 (1878), and ‘Collected Papers,’ p. 13), but appear to have attracted no subsequent attention. This early description has been amplified, and corresponding absorptions have been shown to exist in mixtures of magnesium with rubidium and cæsium.

On the atomic volume relations in certain isomorphous series. III.

1929 ◽  
Vol 22 (124) ◽  
pp. 70-76
Author(s):  
A. F. Hallimond
Keyword(s):  
Alkali Metal ◽  
Internal Pressure ◽  
Alkali Metals ◽  
Alkali Halides ◽  
Atomic Volume ◽  
Free Alkali ◽  
Large Measure ◽  
Accurate Knowledge ◽  
Sodium And Potassium ◽  
Large Contraction

Accurate knowledge of the compressibility of solids was first due in a large measure to the investigations of T. W. Richards, who showed that the pressure-volume curves for sodium and potassium approximate in form to rectangular hyperbolae, that the compressibilities of the free alkali metals are nearly proportional to the atomic volumes, and that the atoms can be treated as filling the available space. Richards then endeavoured to calculate the relative volumes of the combined elements in the alkali halides, assuming that the large contraction which takes place on forming the compound was due to an internal pressure which affected equally the alkali metal and the halogen.

ANIONIC POLYMERIZATION OF STYRENE

1960 ◽  
Vol 38 (10) ◽  
pp. 1891-1900 ◽  
Author(s):  
D. J. Worsfold ◽  
S. Bywater
Keyword(s):  
Absorption Spectra ◽  
Anionic Polymerization ◽  
Benzene Solution ◽  
Activation Energies ◽  
Ultraviolet Absorption ◽  
First Order ◽  
Initiation And Propagation ◽  
Apparent Activation Energies ◽  
Kinetics Of

A study of the kinetics of the initiation and propagation reactions in the polymerization of styrene by butyllithium in benzene solution has been made. The initiation has been shown to be first order in styrene and 0.155 order in butyllithium, the propagation to be first order in styrene and half order with respect to active chain ends. The apparent activation energies of the two reactions have been shown to be 18,000 calories and 14,300 calories respectively. The ultraviolet absorption spectra of colored species produced has been measured and compared with others found in similar systems.

Anionic Polymerization of Vinyl Monomers

1975 ◽  
Vol 48 (3) ◽  
pp. 359-409 ◽  
Author(s):  
Maurice Morton ◽  
Lewis J. Fetters
Keyword(s):  
Special Reference ◽  
Anionic Polymerization ◽  
Alkali Metals ◽  
Good Reason ◽  
Free State ◽  
Vinyl Monomers ◽  
Experimental Conditions ◽  
Group I ◽  
Sodium And Potassium

Abstract Addition polymerizations involving soluble organometallic species have received intensive attention in recent years with special reference to the type of counterion and solvent. An anionic mechanism is proposed for those systems where there is good reason to assume that the metal is strongly electropositive relative to the carbon (or other) atom at the tip of the growing chain. Hence, the metal, e.g. lithium, becomes a cation either in the free state or coupled with the growing carbanion. Under the appropriate experimental conditions, spontaneous termination is avoidable in many of those systems when one of the metals of Group I is used as the counterion. The alkali metals sodium and potassium were revealed to be polymerization initiators of isoprene in the disclosures of Matthews and Strange in 1910 and Harries in 1911. The first unambiguous report of the use of lithium in reactions with diolefins appears to be that of Ziegler and coworkers in 1934. Their work consisted of an investigation of the reaction between the alkali metals (lithium, sodium) or alkyllithium species and butadiene, isoprene, 2,3-dimethylbutadiene, or piperylene.

Diffusion of Alkali Metals in SiC

2014 ◽  
Vol 778-780 ◽  
pp. 297-300 ◽  
Author(s):  
Margareta K. Linnarsson ◽  
Anders Hallén
Keyword(s):  
Mass Spectrometry ◽  
Alkali Metal ◽  
Ion Implantation ◽  
Alkali Metals ◽  
Secondary Ion Mass Spectrometry ◽  
Temperature Range ◽  
Metal Diffusion ◽  
Induced Defects ◽  
Secondary Ion ◽  
Sodium And Potassium

Diffusion of lithium, sodium and potassium in SiC has been studied by secondary ion mass spectrometry. The alkali metal diffusion sources have been introduced by ion implantation. Subsequent anneals have been carried out in vacuum or in Ar atmosphere in the temperature range 700 °C - 1500 °C for 5 min to 16 h. The bombardment-induced defects in the vicinity of the ion implanted profile are readily decorated by the implanted . In the bulk, the diffusing alkali metals are most likely trapped and detrapped at boron and/or other defects during diffusion. The diffusivity of the studied alkali metals decreases as the mass increases, Li+<Na+<K+, but the sodium mobility in SiC is substantial already at 1100 °C.

scholarly journals The absorption spectra of mixed metallic vapours

1924 ◽  
Vol 105 (730) ◽  
pp. 221-225 ◽  
Keyword(s):  
Absorption Spectra ◽  
Alkali Metals ◽  
Molecular Form ◽  
Band Spectrum ◽  
Absorption Bands ◽  
Metal Vapour ◽  
Sodium Potassium ◽  
Physical Conditions ◽  
Sodium And Potassium ◽  
Great Complexity

It has been known for many years that bands of great complexity occur in the absorption spectra of the alkali metals. The extensive absorption bands of sodium vapour in the green and red portions of the spectrum have, in particular, attracted considerable attention. R. W. Wood has discussed fully the structure of these bands, the manner in which they fluctuate with change in certain physical conditions, and their connection with the fluorescence spectrum. The existence of these bands leads to the conclusion that a certain number of the atoms in an alkali metal vapour are associated, though other considerations have indicated that the proportion present in the molecular form cannot be large. It is reasonable to suppose that, in a mixture of the vapours of two alkali metals, "mixed" molecules containing atoms of both elements will "exist" molecules containing atoms of both elements will exist, in addition to these normally present in the unmixed vapours. These "mixed" molecules if present in sufficient number will exhibit an absorption spectrum, probably similar in character to the bands of the simple alkali metals. In the present communication a new band spectrum is described which is developed only in the vapour of mixtures of sodium and potassium and which, it is suggested, is produced by the sodium-potassium molecules present in the mixed vapour.

Pulse Radiolytic Formation of Solvated Electrons, Ion-pairs, and Alkali Metal Anions in Tetrahydrofuran

1974 ◽  
Vol 52 (18) ◽  
pp. 3259-3268 ◽  
Author(s):  
G. A. Salmon ◽  
W. A. Seddon ◽  
J. W. Fletcher
Keyword(s):  
Alkali Metal ◽  
Alkali Metals ◽  
Dissociation Constants ◽  
Alkali Metal Cation ◽  
Ion Pairs ◽  
Alkali Metal Cations ◽  
Solvated Electrons ◽  
Sodium Potassium ◽  
Sodium And Potassium ◽  
Metal Anions

Pulse radiolysis of solutions of alkali metal cations in tetrahydrofuran (THF) demonstrates the formation of solvated electrons es−, alkali metal cation-ion pairs (M+, es−), and alkali metal anions M−. This paper describes the spectra, extinction coefficients, and radiolytic yields of es−, lithium, sodium, potassium, and cesium species in THF. The reaction kinetics are complex but largely involve reactions A and B[Formula: see text]with the concomitant disappearance of all three species by reaction with radiolytically produced radicals. Rate constants and ion-pair dissociation constants for es− and the sodium and potassium species are presented and compared with data established from studies of blue solutions of alkali metals dissolved in THF.

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