Showing papers on "Substituent published in 1981"

Nitrogenous dispersants, lubricants and concentrates containing said nitrogenous dispersants

Abstract: Compositions useful as lubricant and fuel dispersants are prepared by reacting an intermediate (A) of the formulae ##STR1## wherein each R is hydrogen or a lower hydrocarbon-based group, Ar is an aromatic moiety having at least one aliphatic substituent of at least 6 carbon atoms and x is 1 to about 10, with an amino compound (B) which contains one or more amino groups having hydrogen bonded directly to an amino nitrogen.

Inhibitory effect of methyl jasmonate and its related compounds on kinetin‐induced retardation of oat leaf senescence

Abstract: The senescence-promoting activities of methyl jasmonate and its related compounds were compared with respect to structure-activity relationships. The activities were assayed by using oat (A vena saliva L. cv. Victor) leaf segments in the presence of 2 μg/ml kinetin. Dextrorotatory methyl jasmonate prepared from an authentic sample of the racemate mixture was less active than the naturally occurring levorotatory form especially at its low concentrations (0.1 to 2.5 μg/ml). The activity of jasmonic acid, the free acid form of methyl jasmonate, was much less than the methyl ester, and this relationship was true for the other compounds tested. The reduction of the unsaturated bond in the substituent at the C-2 position and the keto group at the C-3 position greatly reduced the activity. The length of the n -alkyl substituents at the C-2 position had also a significant effect on the activity. From these results, it is concluded that the important functional groups for the high senescence-promoting activity of the methyl jasmonate related compounds are the methyl acetate substituent at the C-l position, the 2′cis-pentenyl or n-pentyl group at the C-2, position and the keto group at the C-3 position in methyl jasmonate.

Carbene singlet-triplet gaps. Linear correlations with substituent. pi. donation

Abstract: The singlet-triplet gaps from STO-3G calculations for methylene and 29 substituted methylenes correlate with theoretical and empirical measures of ..pi.. donation by substituents. The ..pi.. donors stabilize the singlet more than the triplet, while ..pi.. acceptors have the opposite effect. Rough estimates of carbene singlet-triplet gaps can be made by using either calculated ..pi.. charges in the corresponding substituted benzene or empirical sigma/sub R//sup 0/ constants.

Factors affecting reactivity in ammonia chemical ionization mass spectrometry

Abstract: Several factors affecting reactivity in ammonia chemical ionization mass spectrometry (NH3 CI) have been examined. These include the sample proton affinity, the preferred site of protonation and [NH4]+ attachment, and substituent effects. In general, compounds having proton affinities ≲787 kJ mol−1 do not yield analytically useful intensities of the [M·NH4]+ adduct ion. Substituted aromatic compounds in which the ring is the most basic site yield little (if any) [M·NH4]+ ion even if the proton affinity of the compound is greater than 787 kJ mol−1. On the other hand, some aromatic compounds in which the substituent is the most basic site yield relatively abundant adduct ions. The spectra of compounds possessing a good leaving group (X) exhibit only weak [M·NH4]+ ions, but intense [M·NH4 − HX]+ and [M − X]+ ions formed by substitution and elimination reactions. Electronic effects strongly influence these processes. Several examples are presented in which isomers are readily differentiated because of different reactivities under ammonia chemical ionization conditions.

Carbon-13 substituent chemical shifts in the side-chain carbons of aromatic systems: the importance of π-polarization in determining chemical shifts

Abstract: 13 C Substituent chemical shifts of the carbonyl sites in the side-chains of meta- and para-substituted benzenes of the type XC6H4COZ have been measured. Analysis of this data using the dual substituent parameter method shows that inductive effects are predominant. The reverse inductive contribution observed is explained in terms of a π-polarization mechanism. Critical support for this mechanism is obtained from additional series where the carbonyl is complexed with Lewis acids. The concepts of ‘extened’ and ‘localized’π-polarization are discussed.

Benzisothiazole and benzisoxazole piperazine derivatives

Abstract: Disubstituted N,N-piperazinyl derivatives are disclosed wherein one substituent is benzisothiazol-3-yl or benzisoxazol-3-yl and the other is alkylene attached to heterocycles such as azaspiro[4.5]decanedione, dialkylglutarimide, thiazolidinedione and spirocyclopentylthiazolidinedione or butyrophenone-like groups. The compounds have psychotropic properties and 8-[4-[4-(1,2-benzisothiazol-3-yl)-1-piperazinyl]butyl]-8-azaspior[4.5]decane-7,9-dione is a typical embodiment having selective antipsychotic activity.

Intramolecular electron transfer and dehalogenation of anion radicals. 4. Haloacetophenones and related compounds

Abstract: Halogen-substituted acetophenones and several other carbonyls and carboxyl derivatives were reduced with e/sub aq//sup -/in irradiated aqueous solutions to produce the anion radicals. In certain cases, reduction by (CH/sub 3/)/sub 2/CO/sup -/ was also used. The anion radicals undergo intramolecular electron transfer and dehalogenation to yield inorganic halide ions. The rates of these reactions varied over a wide range (10/sup 1/-10/sup 7/s/sup -1/) and were strongly dependent on the nature of the halogen and the other substituent and their relative positions in the molecule. The results obtained here are discussed along with previous measurements on cyano and nitro derivatives. The rate of dehalogenation is found to be dependent on the electron affinity of the other substituent on the ring. Hammett's substituent constants do not correlate with the observed rates. However, spin density distribution in the anion radicals, as derived from ESR parameters, yields a good qualitative correlation. Increased spin density on the ring carbon bearing the halogen is accompanied by an increase in the rate of C-X bond scission. The spin density represents in this case the negative charge density, since protonation of the anion radicals in minor changes in spin densities but causes a dramatic decrease of the ratemore » of dehalogenation. 3 figures, 2 tables.« less

The Diels–Alder route to allylsilanes from 1-trimethylsilylbutadienes

Abstract: The synthesis and Diels–Alder reactions of 1-trimethylsilylbutadiene (3) and its 3-methyl (17), 3-trimethylsilyloxy (20), 4-methyl (4), and 4-trimethylsilyl (6) derivatives are reported. The silyl group reduces somewhat the rate of the Diels–Alder reactions, and has, if anything, a small ‘ortho’-directing effect on the regioselectivity in the reactions of (3) with methyl acylate, methyl propiolate, citraconic anhydride, and 2,6-dimethylbenzoquinone. The other substituent in the dienes (17), (20), and (4) is therefore the major influence on the regioselectivity in the reactions of these dienes with methyl acrylate and methyl propiolate. The products of the Diels–Alder reactions of (3), (17), and (4) are allylsilanes, which undergo clean protodesilylation with acid, and, with the acid and ester derived from the maleic anhydride adduct of (3), undergo epoxidation and sulphenylation reactions giving an allyl alcohol (33) and an allyl sulphide (37), respectively. The adducts from (20) can be hydrolysed to β-silylketones, which can be converted into enones by bromination. 1-Pentamethyldisilylbutadiene (15) is no more reactive and no more regioselective than (3). The ‘ortho’-adduct (42) from the reaction of (3) and methyl propiolate aromatises with DDQ to give methyl m-trimethylsilylbenzoate (53) in high yield, in a reaction involving rearrangement of the silyl group, even though a direct dehydrogenation is an available pathway.

The separation of polar and steric effects. Part 14. Kinetics of the reactions of benzoic acid and of ortho-substituted benzoic acids with diazodiphenylmethane in various alcohols

Abstract: The main results now discussed are rate coefficients for the reactions of benzoic acid and 32 ortho-substituted benzoic acids with diazodiphenylmethane (DDM) at 30.0 °C in 11 alcohols including 2-methoxyethanol. The reaction involves a rate-determining proton transfer. The results have been subjected to correlation analysis in two ways. (a) For the reactions of a given acid in the various alcohols, the log k values are correlated through multiple regression on appropriate solvent parameters. (b) For reactions in a given alcohol, the log k values for the various acids are correlated by using the appropriate form of the extended Hammett equation involving inductive, resonance, and steric parameters. Analyses of type (a), as in earlier work, involve the σ* value of the group R in the alcohol ROH, the Kirkwood function of dielectric constant, f(Iµ)=(Iµ– 1)/(2Iµ+ 1) and nγH, the number of hydrogen atoms in the γ-position in the alcohol. These correlations yield information on the influence of ortho-substituents on the relative importance of specific and non-specific solvent effects. In analyses of type (b) the correlation equations are established with a limited set of substituents (up to 18), whose characteristic parameters σI, σR, and v(determined by Charton) are well established, and are unlikely to show effects due to hydrogen-bonding or substituent conformation. The results for other substituents are then interpreted by comparing log k(calc). from a correlation expression with log k(obs.).

Preparation of polyphenols by oxidation of hydroxybenzaldehydes

Abstract: Optionally aldehyde substituted polyphenols are prepared by oxidizing, with hydrogen peroxide, a hydroxybenzaldehyde bearing at least one aldehyde substituent ortho- and/or para- to the nuclear hydroxyl group, in an aqueous reaction medium and in the presence of an alkali or alkaline earth metal base, the process being characterized in that the pH of the reaction medium is continuously maintained at a value no greater than 7 throughout the course of the oxidation reaction. The subject process is well suited for the preparation of, e.g., hydroxy-p-vanillin from guaiacol, and the novel compound 2,4,6-triformylphenol.

13C NMR investigation of some hetero-ring substituted 2- and 4-quinolone systems

Abstract: A series of 2- and 4-quinolones substituted in the hetero-ring have been evaluated using 13C NMR techniques. Substituent effects are discussed as an aid to evaluation of potential tautomerization in the 2-quinolone systems. The observed substituent shifts for systems having a hydroxy function at the 4-position in the 2-quinolones can be explained without implementing the tautomerism to a 4-quinolone.

Aryloxy substituted photographic couplers and photographic elements and processes employing same

Abstract: Couplers of good reactivity contain an aryloxy coupling-off group having in an ortho position a polarizable carbonyl, sulfonyl or phosphinyl substituent group which is free of photographic dye groups and photographic reagent groups.

Method for forming a cyan dye image

Abstract: A method for forming a cyan dye image by developing an exposed silver halide photographic material with a developer containing a color developing agent in the presence of a cyan coupler, wherein the coupler is a 2,5-diacylaminophenol in which each acylamino group has a substituent containing an oxycarbonyl, sulfonyloxy, oxysulfonyl, arylsulfonamide or arylsulfamoyl group or other organic group containing a sulfone group.