Singly-branched hydrocarbons

If both X and Y are alkyl groups, the reference compound is a singly branched hydrocarbon, and it is converted to a doubly branched structural unit in the hypothetical dehydrogenation process hence... 

At higher temperature (>560K), over poisoned or unpoisoned catalyst, increased rates of diffusion of hydrocarbon products allow the shape-selectivity of the catalyst to become apparent. The isomerization reactions within the channels which lead to linear and singly branched hydrocarbons may also occur in reverse on the active sites of the external surface (most active sites at the zeolite surface occur at the mouth of the channels), which may thus mask some of the shape-selectivity of the zeolite. 

The fact that only a relatively small fraction of singly-branched hydrocarbons is produced in the synthesis on iron and cobalt catalysts is very difficult to explain on the basis of the carbide-methylene polymerization hypothesis. Branching should occur whenever a carbidic carbon is included in a methylene polymerization chain, and as there is according to this hypothesis a considerable supply of carbidic carbon, branching should occur much more often than is the case. Furthermore, there is no explanation offered by this hypothesis as to why the branch is limited to a single methyl group. 

The chain and branched chain saturated hydrocarbons make up a family called the alkanes. Some saturated hydrocarbons with five carbon atoms are shown in Figure 18-11. The first example, containing no branches, is called normal-pentane or, briefly, n-pentane. The second example has a single branch at the end of the chain. Such a structural type is commonly identified by the prefix iso- . Hence this isomer is called /50-pentane. The third example in Figure 18-11 also contains five carbon atoms but it contains the distinctive feature of a cyclic carbon structure. Such a compound is identified by the prefix cyclo in its name—in the case shown, cyclopentane. 

Blumer M (1970) Dissolved organic compounds in seawater. Saturated and olefinic hydrocarbons and singly branched fatty acids. In Hood DW (ed) Organic matter in natural waters. Publication no. 1. Institute of Marine Science, University of Alaska, pp 153-167... 

Hydrocarbons (multibranched chain) from singly branched and straight-chain hydrocarbons KBaX Isobutane [152]... 

The form of the isotherms of the mixtures is largely independent of the cation distribution within the cage, i.e., whether the cation-poor or cation-rich model is used. This result is somewhat surprising, especially in view of the different adsorbate structures predicted by single-component isotherms (118-120). Only nonpolar adsorbates were considered in this study and the insensitivity to cation arrangement may well change if one component possesses a permanent dipole. These simulations were based on simple spherical molecules, but the competition for pore space as it depends on size, shape, and polarizability may be extended to other adsorbates. Indeed, Santilli et al. (129) observed experimentally that a branched hydrocarbon adsorbs in preference to a linear one at low loading. 

The pore diameters of MFI-type zeolites are comparable to the size of many commercially important molecules, such as aromatics or linear or branched hydrocarbons [1]. Thus, the study of the difiusion of reactive molecules in the channel system of zeolite catalysts is of considerable interest for the understanding of the catalyst performance. A variety of methods has been developed and applied to the measurement of diffii-sion coefficients, amongst others gravimetric techniques [2], neutron scattering [3], NMR [4] and Frequency Response [5]. The FTIR technique offers the possibility to study sorption and sorption kinetics under conditions close to those of catalytic experiments. By the use of an IR microscope, single crystals have become accessible to the FTIR technique. 

Although thermodynamic calculations show appreciable quantities of di-methylbutanes at equilibrium (about 30-35% of the total hexane isomers at 500°C), such quantities are not observed in reforming. Equilibria are established readily between n-hexane and the methylpentanes, but not between these hydrocarbons and the dimethylbutanes. The reaction kinetics are not favorable for the rearrangement of singly branched to doubly branched isomers (11). This limitation apparently does not exist for the rearrangement of the normal structure to the singly branched structures. 

If alcohols are the precursors of the hydrocarbons in the synthesis, it is probable that a reaction analogous to the 0X0 synthesis occurs on the surface of Fischer-Tropsch catalysts. Such a reaction would account for the relatively small fraction of branched hydrocarbons and for the fact that the branches are almost entirely single methyl groups. 

A hydrocarbon is a compound composed of only carbon and hydrogen. A saturated hydrocarbon bas only carbon-carbon single bonds in the molecule. An unsaturated hydrocarbon has one or more carbon-carbon multiple bonds but may also contain carbon-carbon single bonds. A normal hydrocarbon has one chain of consecutively bonded carbon atoms. A branched hydrocarbon has at least one carbon atom not bonded to the end carbon of a chain of consecutively bonded carbon atoms. Instead, at least one carbon atom forms a bond to an inner carbon atom in the chain of consecutively bonded carbon atoms. 3. In order to form, cyclopropane and cyclobutane are forced to form bond angles much smaller than the preferred 109.5° bond angles. Cyclopropane... 

Any single C saturated hydrocarbon is a substituted methane n times over and a substituted ethane (n-1) times over (or n times over if cyclic), so simple methyl-susbstituted methanes and ethanes are well worth considering. Discussing the significant conformational points of each and considering their use and the limits on their use as models for more highly branched hydrocarbons is therefore important. 

Within the classes of hydrocarbon compounds (linear, singly branched, doubly branched), good correlations between the peak intensities and the percent of the functional group can be obtained. In general, the absorptivity of terminal methyls is higher than that of internal or branched methyls. 

The three branched-chain amino acids (BCAAs), leucine, isoleucine, and valine, are not synthesized in the body, and therefore are classified as essential amino acids that must be supplied in the diet. They are required for protein synthesis and neurotransmitter synthesis. The basic structure of all amino acids consists of an amine (-NHj) group and a carboxyl (-COOH) group attached to a single carbon atom also present is an organic side chain, and it is the structures of these side chains that give the different amino acids their characteristic structures. The structures of the BCAAs are shown in Figure 13.1, and they are so called because they each possess a short, branched hydrocarbon chain as the side group attached to the alpha carbon of the amino acid molecule. They are the only essential amino acids... 

Each bsu shows percentage of carbon in the liquid hydrocarbons of that carbon number, and the sections of the bar show how much of this material is atraif t chain, how much single branched, etc., as detailed in the key. 

Since carbon can only form a total of four bonds, it is possible for a carbon atom to contain one triple bond and one single bond hydrocarbons containing a triple bond are termed alkynes. Alkynes are named in parallel to the alkanes and alkenes, as described previously, and can also be branched and linear. Propyne, also known as methylacetylene, has the condensed formula CHjC CH and is a component of MAPP gas, a tradename of the Petromont, previously of the Dow Chemical Company. MAPP stands for methylacetylene-propadiene propane. Propyne is usually used in combination with oxygen for welding and is about two to four times more expensive than propane. 

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