5 structural isomers of hexane
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In chemistry, isomers (from Greek Î¹ÏƒÎ¿Î¼ÎµÏ�Î·Ï‚, isomerÃ¨s; isos = "equal", mÃ©ros = "part") are compounds with the same molecular formula but different structural formulas. Isomers do not necessarily share similar properties, unless they also have the same functional groups. There are many different classes of isomers, like stereoisomers, enantiomers, geometrical isomers, etc. (see chart below). There are two main forms of isomerism: structural isomerism and stereoisomerism (spatial isomerism).
In structural isomers, sometimes referred to as constitutional isomers, the atoms and functional groups are joined together in different ways. Structural isomers have different IUPAC names and may or may not belong to the same functional group. This group includes chain isomerism whereby hydrocarbon chains have variable amounts of branching; position isomerism which deals with the position of a functional group on a chain; and functional group isomerism in which one functional group is split up into different ones.
In skeletal isomers the main carbon chain is different between the two isomers. This type of isomerism is most identifiable in secondary and tertiary alcohol isomers.
Tautomers are structural isomers of the same chemical substance that spontaneously interconvert with each other, even when pure. They have different chemical properties, and consequently, distinct reactions characteristic to each form are observed. If the interconversion reaction is fast enough, tautomers cannot be isolated from each other. An example is when they differ by the position of a proton, such as in keto/enol tautomerism, where the proton is alternately on the carbon or oxygen.
In stereoisomers the bond structure is the same, but the geometrical positioning of atoms and functional groups in space differs. This class includes enantiomers where different isomers are non-superimposable mirror-images of each other, and diastereomers when they are not.
Diastereomerism is again subdivided into "cis-trans isomers"", which have restricted rotation within the molecule (typically isomers containing a double bond) and "conformational isomers" (conformers), which can rotate about one or more single bonds within the molecule.
An obsolete term for "cis-trans isomerism" is "geometric isomers".
For compounds with more than two substituents E-Z notation is used instead of cis and trans. If possible, E and Z (written in italic type) is also preferred in compounds with two substituents.
Note that although conformers can be referred to as stereoisomers, they are not stable isomers, since bonds in conformers can easily rotate thus converting one conformer to another which can be either diastereomeric or enantiomeric to the original one.
While structural isomers typically have different chemical properties, stereoisomers behave identically in most chemical reactions, except in their reaction with other stereoisomers. Enzymes however can distinguish between different enantiomers of a compound, and organisms often prefer one isomer over the other. Some stereoisomers also differ in the way they rotate polarized light.
Isomerisation is the process by which one molecule is transformed into another molecule which has exactly the same atoms, but the atoms are rearranged. In some molecules and under some conditions, isomerisation occurs spontaneously. Many isomers are equal or roughly equal in bond energy, and so exist in roughly equal amounts, provided that they can interconvert relatively freely, that is the energy barrier between the two isomers is not too high. When the isomerisation occurs intramolecularly it is considered a rearrangement reaction.
Instances of Isomerization
- Isomerizations in hydrocarbon cracking. This is usually employed in organic chemistry, where fuels, such as pentane, a straight-chain isomer, are heated in the presence of a platinum catalyst. The resulting mixture of straight- and branched-chain isomers then have to be separated. An industrial process is also the isomerisation of n-butane into isobutane.
- Trans-cis isomerism. In certain compounds an interconversion of cis and trans isomers can be observed, for instance, with maleic acid and with azobenzene often by photoisomerization. An example is the photochemical conversion of the trans isomer to the cis isomer of resveratrol :
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Answers:hexane 2-methyl pentane 3-methyl pentane 2,2-dimethyl butane 2,3 dimethyl butane And that's it.
Answers:The tertiary alcohol isomers are the most reactive, then secondary, then primary. Structural isomers.
Answers:Hexanal is the aldehyde structure based on a six-carbon chain. The first C atom forms a carbonyl group and is bonded to H on one side and to the second C in the chain on the other side. Suppose you shift the C=O function to the second C atom. You would have H3C-C(=O)-C4H9, which is 2-hexanone or hexan-2-one. Don't forget that the -C4H9 substituent can have three different isomeric forms as well. If you now shift the C=O function to the third C atom, you get H5C2-C(=O)-C3H7, which is 3-hexanone or hexan-3-one. Only one way to make an ethyl group, but there are two isomeric forms of the -C3H7 substituent. Now put the C=O function on the fourth C atom. Is it any different from having it on the third C atom? Same for having the C=O function on the fifth C atom and the second C atom. And of course moving it to the sixth just gives you the same aldehyde structure as if it were on the first C atom. How many isomers does that make altogether (they all have the same molecular formula).
Answers:Only one of those pairs has the same number of carbons in each molecule of the pair! octane = 8 hexane = 6 pentane = 5 butane = 4 each methyl = 1 add 'em up 8, 2+5 1+5, 2+4 6, 2 + 5 5, 3 + 4 only the second pair (2-methylpentane & 2,4-dimethylbutane) have molecules with the same number of carbons. if you draw them out, you'll also notice they have the same number of hydrogens, so they are structural isomers