T-shape

Chlorine trifluoride, CIF3. M.p. — 76°C, b.p. 12°C, T-shaped, a powerful fluorinating agent. 

For interactions between two quadmpolar molecules which have and 0g of the same sign, at a fixed separation r, the angular factor in equation (Al.5.131 leads to a planar, T-shaped stmcture, 0 = 0, 0g = nil, (ji = 0, being preferred. This geometry is often seen for nearly spherical quadmpolar molecules. There are other planar (ij) = 0) configurations with 0 = jr/2-6g that are also attractive. A planar, slipped parallel stmcture,... 

The interplay between favourable reactivity at a collinear geometry and electrostatic forces favouring a T-shaped geometry leads to a bent geometry at the transition state. 

Figure 9.46 Rotational structure of the Ojj bands in the fluorescence excitation spectra of s-tetrazine dimers at about 552 run. Bottom Ojj band of planar dimer. Middle Ojj band of T-shaped dimer with transition in monomer unit in stem of T. Top Ojj band of T-shaped dimer with transition in monomer unit in top of T. (Reproduced, with permission, from Haynam, C. A., Brumbaugh, D. V and Levy, D. H., J. Chem. Phys., 79, f58f, f983)...

Alza Corp. has also developed an iatrauteriae device, Progestasert, designed to release progesterone [57-83-0] by diffusion through a rate-controlling membrane for up to one year. The dmg reservoir is built into a T-shaped device that is inserted intravaginaHy (15). 

Fig. 11. Types of piperack configurations (a) dead-end yard lines enter and leave one end of yard (b) straight-through yard lines can enter and leave both ends of the yard (c) L-shaped yard lines can enter and leave north and east of the plot (d) T-shaped yard lines can enter and leave on three sides of the plot (e) U-shaped yard lines can enter and leave all four sides of the plot (f) combination of I- and T-shaped yard and (g) complex yard piping...

In this exercise, we will examine three alkali metal trifluorides M=K, Na and Cs (drawn from the same study by Tozer and Sosa as Example 6.6). The structure can take on one of two forms, based on the angles 0 and resulting structure is T-shaped (left drawing below) if 0 is significantly greater than distorted structure results (right) ... 

Note that the structural form of each compound is implied by the presence (T-shaped structure) or absence (distorted structure) of the perturbed asymmetric stretching mode at about 550 cm . 

The experimental spectra are interpreted by Tozer and Sosa as follows In the Na compound, the structure is of the form NaF...F2, and it exhibits an absorption due to the complex at 455 cm, with a 460 splitting (this mode is denoted (Oj). For the other two, T-shaped compounds, the two highest frequencies resemble perturbed forms of the symmetric and asymmetric F-F-F stretching modes that we saw in the F3 anion, which we denote (O2 and (O3. The Cs compound exhibits the asymmetric F3 stretching ((O3) at 550 cm", while the K structure exhibits this vibration at 549 cm" along with a weak absorption at 467 cm". The latter may represent a weakly-active symmetric stretch ((03). 

T-shaped Planar MgF2 (rutile) CIF3 BrF3 RICI2... 

Uracil dimers were studied at the MP2 level using the 6-3IG basis with modified polarization functions. Eleven low-energy minima were located Seven of them are H-bonded, one is T-shaped, and three correspond to various stacked arrangements. The most stable structure was found to be the H-bonded dimer with two Ni-H O2-H bonds (Scheme 85) [98JPC(A)6921]. 

Selecting a bit with T -shaped gage teeth reduces the tendency for the bit walk. 

P NMR spectra indicate the T-shape geometry is retained in solution at -30°C but that the molecule is fluxional at room temperature. Rh(PPh3)3 undergoes a range of addition reactions with Lewis bases (CO, PF3, NH3) to afford various 16- and 18-electron species (Figure 2.14). 

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