Jeffrey’s structures

Less common clathrate hydrates formed by compounds other than natural gas guests (such as Jeffrey s structures III-VII, structure T, complex layer structures) and high pressure hydrate phases are also briefly described to provide a comprehensive account of clathrate hydrate structural properties. 

Similar to Jeffrey s hypothetical structure IV, structure H is a hexagonal crystal of space group P6/mmm. However, in contrast to structure IV, structure H comprises 435663 and 51268 cavities in addition to 512 cavities. On the basis of size considerations (including the relative size of the guests, the size of the cages in I-VII, and the unit cell parameters for sH), the structure was incompatible with Jeffrey s structures. Therefore, sH is not one of Jeffrey s (1984) known or hypothetical structures. Single crystal diffraction data for structure H have been obtained by Udachin et al. (1997b, 2002) and Kirchner et al. (2004). 

The unusual cavities in Jeffrey s structure VI (4454,43596273) and structure VII (4668) have been observed only for single terf-butylamine guests and hexafluoro-phosphoric acid (HPF6-6H20) guests, respectively. tm-Butylamine, Me3CNH2 (Jeffrey and McMullan, 1967), is unique among amine hydrates since it forms a true clathrate rather than a semiclathrate. 

As this text is primarily concerned with natural gas hydrates, no further discussion will be given to Jeffrey s structures III-VII and the other unusual structures described above, since as stated previously these structures have yet to be found for natural gas components. 

The less common structures, Jeffrey s structures III—VII, structure T, and complex layer structures have so far only been found for compounds other than natural gas. These compounds form tetragonal (sill), hexagonal (sIV, sV), cubic (sVI, sVII), trigonal (sT), and alternating sI/sH layer structures. 

Jeffrey, S.W., Structural relationships between algal chlorophylls, in Phytoplankton Pigments in Oceanography Guidelines to Modem Methods, Jeffrey, S.W., Mantoura, R.F.C. and Wright, S.W., Eds., UNESCO, Paris, 1997, 566. 

Tabushi et al. (1981) suggested that the 15-hedron (51263) is absent from Figure 2.5 and in all clathrates except bromine due to an unfavorable strain relative to the other cavities in si and sll. In their review of simple and combined cavities, Dyadin et al. (1991) suggested that in addition to the cavities found in si, sll, and sH, there are 4258 and 51263 cavities. In Jeffrey s (1984) list of a series of seven hydrate crystal structures (Table 2.3), additional cavities to those found in si, sll, and sH are 51263, 4454,43596273, 4668. 

Jeffrey s (1984) List of a Series of Seven Hydrate Crystal Structures... 

After crystal structure II was deduced, a definitive x-ray diffraction study of tetrahydrofuran/hydrogen sulfide hydrate was undertaken by Mak and McMullan (1965), two of Jeffrey s colleagues. The crystal consists of a face-centered cubic lattice, which fits within a cube of 17.3 A on a side, with parameters as given in Table 2.2a and shown in Figure 1.5b. In direct contrast to the properties of structure I, this figure illustrates how a crystal structure may be completely defined by the vertices of the smaller 512 cavities. Because the 512 outnumber the 51264 cavities in the ratio 16 8, only 512 are clearly visible in Figure 1.5b. 

Humic and fulvic acids isolation, structure, and environmental role/ Jeffrey S. Gaffney, editor, Nancy A Marley, editor. Sue B. Clark, editor. 

David J. Beebe, Jeffrey S. Moore, Joseph M. Bauer, Qing Yu, Robin H. Liu, Chelladurai Devadoss and Byung-Ho Jo, Functional hydrogel structures for autonomous flow control inside micro-fluidic channels. Nature, 404 (2000), 588-590. 

In Table I we present some information on idealized frameworks, determined from the data on the known structures of gas, peralkylonium salts and tributylphosphine oxide hydrates. The hydrate number can be determined using the data of this Table and taking into account the nature of the guests concerned by Jeffrey s formula [3 ]... 

In Figure 5 the phase diagrams of BU3XO-H0O (X=N,P,As) systems are presented. According to their structural data 16] these hydrates are referred to as semiclathrates in Jeffrey s terms [4]. In spite of the fact that molecules hydrate formers mentioned have big hydrocarbon radicals and clathrate formation with their participation depends on the whole on the hydrophobic interaction, the hydrophilic interaction plays its part, too. The polarity increase of the functional groups CpK for oxides (CH3)3X0 equals to 4.5 [31], -0.5 [32] and 3.7 [31] for X=N,P and As, respectively) facilitates polyhydrate formation. 

Fookes, C.J.R. and Jeffrey, S.W. (1989) The structure of chlorophyll c3, a novel marine photosynthetic pigment. J. Chem. Soc. Chem. Commun., 1827-1828. 

Jeffrey, P.D., Gorina, S., Pavletich, N.P. Crystal structure of the tetramerization domain of the p53 tumor suppressor at 1.7 Angstroms. Science 267 1498-1502, 1995. 

The main remit of this chapter is to provide reference and plant source details of new flavone and flavonol 0-glycosides discovered since 1991, i.e., covering the years 1992 to 2003. A checklist of all (as far as possible) known structures is also included in Appendices A and B. A series of reviews, which include most of the data on new 0-glycosylflavones and flavonols presented here, have appeared in Natural Product Reports and cover the years 1992 to 1994, 1995 to 1997, and 1998 to 2000, and with a fourth (2001 to 2003) " in press. Other useful sources of data are The Phytochemical Dictionary,The Handbook of Natural Flavo-noids, and for general background reading Jeffrey Harborne s Comparative Biochemistry of the Flavonoids. 

Cho, Y, Gorina, S., Jeffrey, P.D. and Pavletich, N.P Crystal structure of a p53 tumor suppressor-DNA complex understandung tumorigenic mutations (1994) Science 265, 346-355... 

Tittiger C., Barkawi L. S., Bengoa C. S., Blomquist G. J. and Seybold S. J. (2003) Structure and juvenile hormone-mediated regulation of the HMG-CoA reductase gene from the Jeffrey pine beetle, Dendroctonus jejfreyi. Mol. Cell. Endocrin. 199, 11-21. 

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