Donor, primary/secondary

Since phenol has an appreciable dipole moment, and no low energy acceptor orbitals, it should interact best with the donors that have the largest lone pair dipole moment — the oxygen compounds. Iodine has no dipole moment and the interaction with iodine is expected to be essentially covalent. Iodine should interact best with the donors that have the lowest ionization potential, i.e., the ones whose charge clouds are most easily polarized. Similar considerations have been employed to explain the donor strengths of primary, secondary and tertiary amines 35a) and the acid strengths of (35b) ICl, Bt2, I2. CeHsOH and SO2. 

The second important feature of the reaction mechanism of the epoxy compound curing under the action of amines (primary, secondary and tertiary) and their mixtures consists in formation of various hetero-, auto-, inter- and intramolecular donor-acceptor complexes between the components of the reaction system — the starting substances and reaction products. Consideration of this complex formation can adequately explain the reaction kinetics. 

Conformations of primary, secondary, and tertiary amides of (R,R)-tartaric acid, both symmetrically and asymmetrically substituted, have been studied ciys-tallographically [22, 24, 29, 30-40] Moreover, ab initio studies up to MP2 / 6-31G //RHF/6-31G level [41] for both the diamide and N,N,N ,N -tctramcthyl-diamide of (/ ,/ [-tartaric acid have been carried out [20, 22]. X-ray results have shown that primary and secondary amides of (R,R [-tartaric acid tend to adopt a conformation with the extended carbon chain - the Taa structure. In this Taa conformation both the a-hydroxy-amide moieties form planes and the structure gains stabilization from hydrogen bonding between donors, the NH, and acceptors, the proximal OH groups. Moreover, the Taa structure is favorably stabilized by the attraction of antiparallel local dipoles formed along distal C H and Csp2=0 bonds [18, 21, 22],... 

S-Donor Ligands. Dance157,158 has examined the adducts formed between cobalt dithiolenes, [CoL2]2 [L = (CF3)2C2S22 and (NC)2C2S22 (mnt)], and primary, secondary, tertiary, and heterocyclic unidentate and bidentate amines in both solution and the solid state. Both five- and six-co-ordinate adducts are formed. Novel structures result from Co(mnt)22- and [Co(mnt)2]22- with 1,4-disubstituted pyridinium cations in which the anions are sandwiched between two cations, and anion cation charge-transfer spectra have been measured.159... 

Refluxing or photolytic treatment of O-acyl esters (2) in the presence of a hydrogen donor such as Bu3SnH or ter -BuSH, provides the corresponding reduction products via alkyl radicals. This reaction can be applied to primary-, secondary-, and tertiary-alkyl chained carboxylic acids, and can also be used for steroids, sugars, and peptides as shown in eq. 8.4 [9-14]. Racemization does not occur at other chiral centers. 

The scope of the reaction includes the formation of five-, six-, and seven-membered heterocycles from primary, secondary, and aromatic amines as the starting compounds, giving exclusively the exo-methyl product in agreement with Markovnikov s rule. All reactions are found to proceed equally well in toluene, benzene, pentane, and related hydrocarbon solvents. In donor solvents such as THF, catalytic rates are significantly slower. In the series of bisfpenta-methylcyclopentadienyl)lanthanide catalysts, the highest activity was observed with lanthanum and with lutetium the lowest the variation of TON spans over three orders of magnitude. 

AH - EPR signal linewidth AT/T - relative change in transmission D - electron donor, or secondary electron donor D - alternative designation for the primary electron donor cf. P ... 

There are four comprehensive reference texts on phosphine coordination chem-istry. Two are somewhat out-of-date, but the article by Levason is more recent. However, all four give much useful information on synthetic procedures for the preparation of primary, secondary and tertiary phosphines diphosphines multidentate and macrocyclic phosphines mixed Group 15 donor and mixed Group 15/16 donor systems and phosphorus-containing heterocycles. The coordination chemistry of phosphorus has expanded to include P4 fragments, Pg rings, and even naked phosphorus atoms, for example, nine-coordinate P and -Pg systems. ... 

Hydrogen atom donors such as non-nucleophilic tertiary thiols or tri-n-butyltin hydride are extremely efficient traps for the capture of the alkyl radical R derived from O-acyl thiohydroxamates, thus providing a very efficient method for reductive decarboxylation (Scheme 3). In practical terms, the use of the mercaptan is preferred since the tertiary alkyl pyridyl disulfide can be easily removed during work up by a simple acid extraction. The reaction has been successfully applied to a very wide range of complex substrates [8] possessing primary, secondary, or tertiary aliphatic carboxylic acids, and reactions at room temperature or below require only photolysis from a simple tungsten lamp and often involve in situ O-acyl thiohy-droxamate derivatization. 

Steric effects in oxidation are found primarily in the H-atom donor as, for example, isobutane versus 2,4-dimethylpentane where both co-oxidation and added hydroperoxide measurements indicate isobutane to be 1.4 times as reactive toward either R02 radical [38,39], For a series of branched alkanes, the value of kp was more sensitive to changes in steric bulk on the adjacent carbon than on the same carbon but all values were within a factor three [39], Increasing size in f-R02 radicals has little effect on the value of kp for H-atom transfer from primary, secondary or tertiary sites [69]. However, kp for a given hydrocarbon does increase by a factor of about 5—10 as R02 is changed from a tertiary to secondary or primary ROa [78], Moreover, in the oxidation of aromatic compounds, the ratio of kp s for H-atom transfer to parent R02- and to f-Bu02-correlate with meta substituent constants which suggests that this difference in reactivity is due mainly to polar effects [86]. 

By contrast, with the armed donor 85 secondary disaccharides 88 and 91 were the major products, 46 and 27% respectively. Notably in the reaction with 88, no primary disaccharide was detected. 

The studies in Scheme IS indicate that selectivity between primary and secondary hydroxyls is donor dependent, NPOEs and disarmed donors fevoring primary, while armed donors favor secondary. 

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