Singly-branched hydrocarbons structure

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... 

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. 

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. 

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. 

Saturated hydrocarbon A hydrocarbon having only carbon-carbon single bonds. Its structure may be straight or branched. 

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... 

One large and structurally simple class of hydrocarbons includes those substances in which all the carbon-carbon bonds are single bonds. These are called saturated hydrocarbons, or alkanes. In the alkanes the carbon atoms are bonded to each other in chains, which may be long or short, straight or branched. 

We have already remarked that ethane is a member of a family of compounds called the saturated hydrocarbons. This term identifies compounds that contain only carbon and hydrogen in which all bonds to carbon are single bonds formed with hydrogen or other carbon atoms. They occur in chains, branched chains, and cyclic structures. 

A single-carbon branch within a hydrocarbon is referred to as a methyl group, while a two-carbon branch is referred to as an ethyl group. What then is the formal name for the structure shown in exercise 51 ... 

Hydrocarbon frameworks rarely consist of single rings or chains, but are often branched. Rings, chains, and branches are all combined in structures like that of the marine toxin palytoxin that we met at the beginning of the chapter, polystyrene, a polymer made of six-membered rings dangling from linear carbon chains, or of p-carotene, the compound that makes carrots orange,... 

Over 85% of the millions of known compounds are carbon compounds, and a separate branch of chemistry, organic chemistry, is devoted to the study of them. Why are there so many organic compounds The discussion of hydrocarbons and their structural and geometric isomers in Chapter 12 indicates two reasons (1) the ability of many carbon atoms to be linked in sequence with stable carbon-carbon single, double, and triple bonds in a single molecule and (2) the occurrence of isomers. A third reason will be discussed further in this chapter the variety of functional groups that bond to carbon atoms. 

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