Molecular structure cyclic amines

The structure of monomorine I (16a), isolated from the extract of workers of the thief ant, Monomorium pharaonis, by gas-liquid chromatography (Table II), has been revealed to be 3-butyl-5-methyloctahydroindolizidine on the basis of mass and H-NMR spectra. The mass spectmm shows characteristic peaks at m/z 180 (345 M - CH3) and m/z 138 (346 M - Bu, a base peak), indicating the presence of methyl and butyl group attached to the a carbons of an amine, in addition to a molecular ion at m/z 195. The fact that the (M — 1) peak is higher than the M peak indicates a cyclic amine. The H-NMR spectmm shows two methyl groups (triplet at 8 0.88, CH3—CH2 doublet at 8 1.18, CH3CH—N) and three methines adjacent to nitrogen (8 2.13, 2.27, and 2.52). 

DIAMINES AND HIGHER AMINES, ALIPHATIC. The aliphatic diamine and polyaminc family encompasses a wide range of multifunctional. mullireactivc compounds. This family includes ethylenediamine I EDA) and its homologues. the polyethylene polyamines (commonly referred to as ethyleneainines). the diaminoprnpancs and several specific alkancdiamines. and analogous polyamines. The molecular structures of these compounds may be linear, branched or cyclic, or combinations of these. 

To confirm the inclusion mode for a sec. amine, the 1 1 piperidine 4 (n = 1) complex was isolated and its molecular structure was determined by X-ray analysis (Fig. 10) [22], The chromophore is planar (except the o-nitro group) within 0.1 A, to which the cyclic polyether ring extends perpendicularly. The protonated piperidine having a chair form structure is placed on the crown ring and stabilized by very short N+ —H—O- (2.65 A) and N+ —H—O (2.93 A) hydrogen bonds, and two N + —O ion-dipole interactions (3.17 and 3.16 A). The remaining ether oxygen, 0(2), seems to be ineffective on the complexation. 

A large number of structurally characterized bis(trimethylsilyl)amido complexes now exist Table 5 gives a representative selection of monometallic homoleptic compounds, both base-free and with coordinated ethers. Other examples are known with coordinated fiuorobenzenes, isonitriles,methylated pyridines, various amines (TMEDA, PMDTA, TMPDA (Tetra-methylpropylenediamine), BzNMe2 (benzyldimethylamine)), Ph PO, (Bu"0)(Pr )C0, and l,3-(Pr )2-3,4,5,6-tetrahydropyrimid-2-ylidene. Their structures illustrate the complex interactions between metal size, ligand bulk, and molecular structure that exist with these metals. For example, among the alkali metal base-free species, the unsolvated Li derivative crystallizes as a cyclic trimer, whereas the Na salt is found both as a trimer " and as infinite chains of [Na-N(SiMe3)2—] units. The potassium, rubidium, and caesium derivatives exist as discrete dimers in the solid state, constructed around planar [M—N-]2 frameworks. 

The E-isomer is generally more stable than the Z-isomer due to diminished steric hindrance, so it is assumed that the E-isomer is the major product (shown for 83). Water, a reaction by-product, may be removed to give a better yield of product and azeotropic distillation is used as well as molecular sieves (see Section 18.6.3). Enamines are structurally related to an end (HO—C=C) in that the heteroatom is directly attached to the alkene unit. Enamines are often isolable compounds, whereas enols tautomerize spontaneously to the carbonyl form. Note that when imine 76 is formed from iminium salt 80, there is no enamine product. In fact, the C-H in 80 is much less acidic that the N-H unit, so the product is the imine rather than the enamine. It is noted that there is an equilibrium between an imine and an enamine, known as imine-enamine tautomerism, but it will be ignored in this book. Many different secondary amines can be used in this reaction, including cyclic amines (see Chapter 26, Section 26.4.1) such as pyrrolidine (90), piperidine (91), and morpholine (92). It is important to note that it is generally easier to form an enamine from a ketone than from an aldehyde. 

Table 10.6 lists the physical properties of six amide-type solvents, two cyclic morpholines (amine-ether structures) and the low molecular weight... 

Anionic polymerization techniques were also critical for the synthesis of a model cyclic triblock terpolymer [cyclic(S-fo-I-fr-MMA)] [196]. The linear cctw-amino acid precursor S-fr-I-fr-MMA was synthesized by the sequential anionic polymerization of St, I and MMA with 2,2,5,5-tetramethyl-l-(3-lithiopropyl)-l-aza-2,5-disilacyclopentane as the initiator and amine generator, and 4-bromo-l,l,l-trimethoxybutane as a terminator and carboxylic acid generator. Characterization studies of the intermediate materials as well as of the final cyclic terpolymer revealed high molecular and compositional homogeneity. Additional proof for the formation of the cyclic structure was provided by the lower intrinsic viscosity found for the cyclic terpolymer compared to that of the precursor. 

The structural elucidation of mucronine-A-aldehyde (85) (39) (Scheme V) relies upon the peaks at m/e 510 (0.2%), m/e 206 (100%), and m/e 361 (11%). The first named is the molecular ion and reveals the former cyclic structure of the alkaloid. a-Fragmentation at the tertiary amine forms the fragments b and c which indicate a nuclear substituted A,A-dimethylphenylalanine unit in mucronine-A aldehyde. 

It has been reported that the effectiveness of copolymerized DOPO-type monomers can be further improved if the alcohol-amine derivatives of DOPO, for example, Structure 5.11, are used rather than similar structures not containing nitrogen.30 Of the FR fibers based on P-containing comonomers, it has been found that those based on Structure 5.10 are more hydrolytically stable, presumably because the P-containing group is in a cyclic structure and also should the hydrolysis of the P-0 bond occur, it will not lead automatically to a marked reduction in molecular weight.31 All the P-modified PETs appear to be subject to both the vapor-and condensed-phase mechanisms of flame retardance, with the former predominating.32 33... 

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