Trans- PIP

For trans-PIP, pa may also be written as (for details, see original paper ... 

Bhowmick et al. [1986] investigated properties of cis- and trans-polyisoprene blends (cPI/tPI), with a rather cursory look at the effect of gamma irradiation (Table 11.9). The blends consisted of guayule mbber (cPI) and synthetic tPI (Trans-PIP from Polysar). The blends were prepared by mixing the two polymers, along with the typical... 

Birman has also shown that trans-cinnamyl type allylic sec-alcohols can be efficiently resolved using his CF3-PIP catalyst 25 (s = 6-26) or Cl-PIQ catalyst 26 (s = 17-57 see Scheme 8.5) [107]. Additionally, as noted earlier, Maruoka s NHC catalyst 29b was shown to resolve two trans-cinnamyl-type allylic sec-alcohols efficiently (s = 16 and 22 see Scheme 8.8). 

Pyrolysis-gas chromatography was used to determine the degradation of peptides to diketopiperazines (among them Pip-Sar and cis- and trans-Wal-Pip, like 48) for sequence determination in actinomycins [71JCS(CC)39],... 

The sulfonation of low molecular weight model olefins was undertaken to determine the feasibility of this approach. Competitive sulfonations using acetyl sulfate were carried out on the model compounds below, representing the repeat structures of cis-l,4-polyisoprene (PIP), cw-l,4-polybutadiene (c-PBD), and trans-l,4-polybutadiene (Z-PBD), respectively. It was necessary to model both the cis and trans isomeric forms of 1,4-polybutadiene, since ttey have a nearly equal probability of occurrence when the anionic polymerization (Ii counterion) is conducted in a nonpolar hydrocarbon medium... 

Although NCS is S bound in the solid state of trans-[Ir(pip)4(NCS)2]BPh4 (pip = piperidine), it is N bound initially in solution and in the solid state when NCS is the counter-ion. With both counter-ions prolonged aging of solutions yields the S-bound complex. The M—O bond is retained during the reaction of [Ir(NH3)50H] and propionic anhydride to give the propionate complex. Iridium(iii) complexes of 3,3 -diamino-4,4 -dihydroxy-diphenylsulphone and R X=NR (X = N or CH), IrHCl(N—C)(PR3)2, have been isolated. 

Polymer Preparation. Two bifunctional (telechelic) polymers were used in this study. Carboxy-telechelic polybutadiene (PB) is commercially available from B. F. Goodrich (Hycar CTB 2000X156) with molecular characteristics of Mn=4,600, Mw/Mn= 1.8, functionality 2.00 and cis/trans/vinyl ratio of 20/65/15. Carboxy-telechelic polyisoprene (PIP) was prepared by anionic polymerization in THF at -78°C with a-methylstyrene tetramer as a difunctional initiator. The living macrodianions were deactivated by anhydrous carbon dioxide. Five polymers werejjrepared with Mn=6,000 10,000, 24,000, 30,000 and 37,000 having Mw/Mn=sl.l5 a microstructure ratio of 3, 4/1, 2 of 65/35, respectively, and a functionality >1.95. 

Among other proline analogs such as 13-17 shown in Fig. 11.4, NMR analysis of the N-acetyl derivatives of 13-16 in neutral solutions did not reveal any significant difference in the trans/cis ratio compared with N-acetyl-proline except for 5-oxo-proline (15) which exhibits an exclusive trans-amide conformation [63]. However, when replacing proline in Ala-Pro-pNA with Aze (13) and Pip (14) the cis-amide content was 20% and 13%, respectively, compared with 6% for the Pro-peptide. Rates of CTI were accelerated 14.5- and 49-fold relative to the Pro-peptide [64]. 

The different propensities of the alkylated proline analogs Tbp and Dmp for the cis conformation were recently exploited to modulate the activation of 5-hydroxy-tryptamine type 3 receptor upon site-specific incorporation of these residues at the place of a critical proline residue. A direct comparison of Pro, Pip, Aze, Tbp, and Dmp at a defined position of the loop between the second and third transmembrane helices allowed to correlate directly the intrinsic ds-to-trans energy gap of these residues with the activation of the channel [81]. 

Time-resolved IR spectroscopy was used to identify cis and trans isomers [W(C0)4L(S)J, L = PPh3, P(0-i-Pr)3, or P(OEt)3 and S = heptane. These isomers were prepared by photolysis of [W(CO)5L] and cw-[W(CO)4L(pip)]. In heptane the cis isomer is shorter lived than the trans isomer there is no evidence for interconversion of the two. The two isomers react with CO with different rates, and the rate increases with the size of L. The term Token Ligand is coined to indicate that there is a specific interaction between a solvent molecule and what would otherwise be a vacant coordination site. Reactions of ds-[W(CO)4L(pip)] with L, L and V = phosphine or phosphite, proceed by reversible pip dissociation, forming square-pyramidal [W(CO)4L] in which L is equatorially coordinated. The general reaction sequence is given in Scheme 6. Dissociative loss of chlorobenzene from ci5-[W(C0)4 P(0-/-Pr)3 (PhCl)] displays activation parameters of A/Zj = 13.0 kcal mol and ASf = -f 5.6 cal K" mol". Rate constants for thermal reactions of ci5-[W(CO)4(L)(PhCl)] with P(0-f-Pr)3, given in Table 10.5, are predominantly... 

Measurement of Trans-membrane Potential. For a constant bias potential, negligible current flows through the insulator on the semiconductor chip, so that there is no steady state potential across Rm- The potential across the chip is y - Vm. If in the absence of the membrane an photocurrent inflection point potential was measured at S = pip/ then in the presence of the membrane it will shift positive by the value of the trans-membrane potential as indicated by Equation 3. Measuring Vm is clearly analogous to using the sensor to make pH or redox measurements. 

T. R. Hinklin, S. S. Neo, K. W. Chew and R. M. Laine, Precursor Impregnation and Pyrolysis (PIP) Processing of Barium Aluminosilicate-Nicalon Composites, Ceram. Trans. 74, 117-128(1996). 

---