EasyChemistryHigh School (11–12)Organic Chemistry: Some Basic Principles and Techniques › Classification, IUPAC Nomenclature and IsomerismNumericalA-LevelIB
Draw every isomer of C₅H₁₂ and name each…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
Draw every isomer of and name each. How many are there? How many carbon atoms are in the longest chain of the most branched one?
Need a reminder? The key ideaShow
Isomers have the same molecular formula and different structures. Structural: chain, position, functional group, metamerism, tautomerism. Stereo: geometrical (each end of a double bond has two different groups) and optical (a carbon with four different groups). Degrees of unsaturation: . Up to stereoisomers for n different stereocentres.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. Five in a chain. is pentane.
Step 2. Four in a chain. One carbon is a branch. It cannot go on carbon 1, which would make the chain longer. On carbon 2 it gives , 2-methylbutane. Carbon 3 gives the same molecule, numbered from the other end.
Step 3. Three in a chain. Both extra carbons go on the middle carbon. This gives , 2,2-dimethylpropane.
Step 4. Count. There are three isomers. The most branched one has a longest chain of 3 carbons.
Answer: 3 isomers, and a longest chain of 3 carbons.
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