Isomers sentence example
Three isomers exist, the orthoand para-compounds being the chief products of the direct nitration of toluene.
Di-derivatives x x x p v as $ v as s Here we have assumed the substituent groups to be alike; when they are unlike, a greater number of isomers is possible.
In the case of tetra-substituted compounds, thirty isomers are possible when all the groups are different.
Thus in the tri-substitution derivatives six isomers, and no more, are possible when two of the substituents are alike; for instance, six diaminobenzoic acids, C 6 H 3 (NH 2) 2 000H, are known; when all are unlike ten isomers are possible; thus, ten oxytoluic acids, C 6 H 3 -CH 3.
It is found that isomers have nearly the same critical volume, and that equal differences in molecular content occasion equal differences in critical volume.Advertisement
Recent researches have shown that the law originally proposed by Kopp - " That the specific volume of a liquid compound (molecular volume) at its boiling-point is equal to the sum of the specific volumes of its constituents (atomic volumes), and that every element has a definite atomic value in its compounds " - is by no means exact, for isomers have different specific volumes, and the volume for an increment of CH 2 in different homologous series is by no means constant; for example, the difference among the esters of the fatty acids is about 57, whereas for the aliphatic aldehydes it is 49.
A factor of considerable importance in determining boiling-points of isomers is the symmetry of the molecule.
Sodium percarbonates of the formulae Na 2 CO 4, Na2C206, Na 2 C05, NaHCO 4 (two isomers) are obtained by the action of gaseous or solid carbon dioxide on the peroxides Na 2 0 2, Na 2 0 3, NaHO 2 (two isomers)in the presence of water at a low temperature (R.Wolffenstein and E.Peltner, Ber., 1908, 41, pp. 275, 280).
It is seen that aldoses and ketoses which differ stereochemically in only the two final carbon atoms must yield the same osazone; and since d-mannose, d-glucose, and d-fructose do form the same osazone (d-glucosazone) differences either structural or stereochemical must be placed in the two final carbon atoms.3 It may here be noticed that in the sugars there are asymmetric carbon atoms, and consequently optical isomers are to be expected.
The crude cresol obtained from tar cannot be separated into its different constituents by fractional distillation, since the boiling points of the three isomers are very close together.Advertisement
Pimaric acid closely resembles abietic acid into which it passes when distilled in a vacuum; it has been supposed to consist of three isomers.
The one group included those isomers where the identity in composition was accompanied by identity in molecular weight, i.e.
Consequently, of each pair of isomers we may establish beforehand which is the more stable; either in particular circumstances, a direct change taking place, as, for instance, with maleic acid, which when exposed to sunlight in presence of a trace of bromine, yields the isomeric fumaric acid almost at once, or, indirectly, one may conclude that the isomer which forms under greater heat-development is the more stable, at least at lower temperatures.
Nevertheless, the theoretical possibility, and its realization in many cases, has brought considerations to the front which have recently become of predominant interest; consequently the possible transformations of isomers and polymers will be considered later under the denomination of reversible or dynamical isomerisms.
The constitution of these inorganic isomers is still somewhat questionable; and in addition it seems that polymerism, metamerism and stereoisomerism play a part here, but the general feature is that cobalt and platinum act in them with high valency, probably exceeding four.Advertisement
Now, in this case, the first definition expresses much better the whole chemical behaviour of ozone, which is that of "energetic" oxygen, while the second only includes the fact of higher vapour-density; but in applying the first definition to organic compounds and calling isobutylene "butylene with somewhat more energy" hardly anything is indicated, and all the advantages of the atomic conception - the possibility of exactly predicting how many isomers a given formula includes and how you may get them - are lost.
The third most valuable indication which molecular structure gives about these isomers is how to prepare them, for instance, that normal hexane, represented by CH 3 CH 2 CH 2 CH 2 CH 2 CH3, may be obtained by action of sodium on propyl iodide, CH 3 CH 2 CH 2 I, the atoms of iodine being removed from two molecules of propyl iodide, with the resulting fusion.
An example may prove this, but before quoting it, the question of determining b must be decided; this results immediately from the above quotation, b being the volume Vat the absolute zero (T =0); so the volume of isomers ought to be compared at the absolute zero.
Certain investigations on isomerism which have become especially prominent in recent times bear on the possibility of the mutual transformation of isomers.
These laws have the advantage of being applicable to the mutual transformations of isomers, whatever be the nature of the deeper origin, and so bring polymerism, metamerism and polymorphism together.Advertisement
In ordinary isomers indications of mutual transformation often occur; and among these the predominant fact is that denoted as tautomerism or pseudomerism.
These isomers may frequently be distinguished by the facts that the cis-acids yield anhydrides more readily than the trans-acids, and are generally converted into the trans-acids on heating with hydrochloric acid.
Three structural isomers are possible.
Many polymerize readily, or are transformed into isomers by boiling with dilute alcoholic sulphuric acid.
Candidates should be able to show an understanding of isomerism by predicting some of the structures of the isomers of given higher alkanes.Advertisement
Both can be formed in cracking pentane or higher alkanes in which various isomers of C 5 H 10 would be formed.
Where you have isomers, the more branched the chain, the lower the boiling point tends to be.
It's extremely important to draw the isomers correctly.
Drawing structural formulae for the last pair of models gives two possible isomers.
Compounds that have the same formula but differ in their atomic positions, like these two, are called isomers.Advertisement
For a real PES, there are permutational isomers of each minimum.
Trans and positional isomers are formed during this process, and these are found in depot fat and milk fat.
It is easy to miss geometric isomers in an exam.
For example, there are two structural isomers with the molecular formula C 3 H 7 Br.
I have put models of the chain isomers of pentane here.Advertisement