Constitutional isomers alkanes, number

They have the same molecular mass, but differ in their manner of linkage, their branching, and in the order (sequence) of their atoms (constitutional isomers). The number of possible isomers increases rapidly in higher generations - by analogy with the classical case of the alkanes. 

Compounds like the two C4M [() molecules and the three C3I I 12 molecules, which have the same formula but different structures, are called isomers, from the Greek isos + meros, meaning "made of the same parts." Isomers are compounds that have the same numbers and kinds of atoms but differ in the way the atoms are arranged. Compounds like butane and isobutane, whose atoms are connected differently, are called constitutional isomers. We ll see shortly that other kinds of isomers are also possible, even among compounds whose atoms are connected in the same order. As Table 3.2 shows, the number of possible alkane isomers increases dramatically as the number of carbon atoms increases. 

The maximum number of possible constitutional isomers increases dramatically as the number of carbon atoms in the alkane increases, as shown in Table 4.1. For example, there are 75 possible isomers for an alkane having 10 carbon atoms, but 366,319 possible isomers for one having 20 carbons. 

The number of constitutional isomers increases rapidly as the number of carbon atoms in saturated hydrocarbons increases. There are live isomeric alkanes (Table 27-3). 

TABLE 27-4 Numbers of Possible Constitutional Isomers of Alkanes... 

One caveat of the equations is that there can be no more than one chlorine atom bound to any carbon atom. This was imposed because, although free-radical chlorination has low positional selectivity, a second chlorine atom does not readily substitute for a hydrogen at a carbon already bound to chlorine [13-15]. Table 1 shows the number of constitutional isomers for a number of chlorinated alkanes. 

Two or more compounds with the same molecular formula but different properties are called isomers. Isomers with different arrangements of bonded atoms are constitutional (or structural) isomers alkanes with the same number of C atoms but different skeletons are examples. The smallest alkane to exhibit constitutional isomerism has four C atoms two different compounds have the formula C4H10, as shown in Table 15.3 on the next page. The unbranched one is butane (common name, /t-butane n- stands for normal, or having a straight chain), and the other is 2-methylpropane (common name, i obutane). Similarly, three compounds... 

The number of constitutional isomers increases rapidly as the number of carbons in an alkane increases. For example, there are 75 alkanes with molecular formula C10H22 and 4347 alkanes with molecular formula C15H32. To avoid having to memorize the names of thousands of stmctural units, chemists have devised rules that name compounds on the basis of their structures. That way, only the rules have to be learned. Because the name is based on the structure, these rules make it possible to deduce the structure of a compound from its name. 

Constitutional isomers, 22, 45, 172, 291 of alkanes, number of, 60 table Coordination polymerization, 246, 383, 567-570, 573 Copolymer, 383 Copper (1) salts... 

Robinson, Harary and Balaban [54], by plying Pdlya s theorem and Otter s dissimilarity characteristic equation [85], presented for the first time recurrence formulas for counting the achiral isomers of alkyl radicals and alkanes. If the constitutional isomers of alkanes are denoted by Vn (quartic trees), and if their number, including stereoisomers, is denoted hy fn (steric trees), the latter number may be decomposed into achiral (tn) chiral (cn) ismners. The numbers fcH n = 1-14 are presented in Table 3 ... 

Open-chain aliphatic hydrocarbons constitute alkanes, alkenes, alkynes, and their isomers. Alkanes have the general formula C H2 +2, where n is the number of carbon atoms in the molecnles, snch as methane, propane, n-pentane, and isooctane. Alkenes or olefins are nnsaturated compounds, characterized by one or more double bonds between the carbon atoms. Their general formula is C H2 . Examples are ethylene, 1-butene, and... 

Constitutional isomers, as stated earlier, have different physical properties. The differences may not always be large, but constitutional isomers are always found to have different melting points, boiling points, densities, indexes of refraction, and so forth. Table 4.1 gives some of the physical properties of the CeHi4 isomers, of which there are only five. Note that the number of constitutional isomers that is possible increases dramatically as the number of carbon atoms in the alkane increases. 

Number of C-atoms in alkanes Number of possible constitutional isomers... 

With alkanes that have more than one kind of hydrogen, free radical halogenation will usually lead to a mixture of constitutional isomers. Which isomer dominates will depend upon the relative reactivity and number of different hydrogens that can be abstracted. Whi le the structure of the substrate determines which sites are the more reactive, the quantitative selectivity of a reaction will depend upon the reactivity of the halogen radical atom. 

For an alkane, the number of possible constitutional isomers increases with increasing molecular size. Table 4.4 illustrates this trend. 

The large numbers in Table 4.2 are based on calculations that must be done with a computer. Similar calculations, which take into account stereoisomers (Chapter 5) as well as constitutional isomers, indicate that an alkane with the formula C167H336 would, in theory, have more possible isomers than there are particles in the observed universe ... 

Table 2 3 lists the heats of combustion of several alkanes Unbranched alkanes have slightly higher heats of combustion than their 2 methyl branched isomers but the most important factor is the number of carbons The unbranched alkanes and the 2 methyl branched alkanes constitute two separate homologous senes (see Section 2 9) m which there is a regular increase of about 653 kJ/mol (156 kcal/mol) m the heat of combustion for each additional CH2 group... 

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