![]() Such compounds are composed only of carbon and hydrogen atoms bonded together by sigma bonds (all carbons are sp 3 hybridized).Īn excellent presentation of organic nomenclature is provided on a Nomenclature Page. Names of substituent groups, other than hydrogen, that complete the molecular structure.Īs an introduction to the IUPAC nomenclature system, we shall first consider compounds that have no specific functional groups. A suffix or other element(s) designating functional groups that may be present in the compound. A root or base indicating a major chain or ring of carbon atoms found in the molecular structure. In general, an IUPAC name will have three essential features: Likewise, given a IUPAC name, one should be able to write a structural formula. Knowing these rules and given a structural formula, one should be able to write a unique name for every distinct compound. ![]() ![]() The IUPAC nomenclature system is a set of logical rules devised and used by organic chemists to circumvent problems caused by arbitrary nomenclature. Since hydrogen is such a common component of organic compounds, its amount and locations can be assumed from the tetravalency of carbon, and need not be specified in most cases. Second, it should identify and locate any functional groups present in the compound. First, it should indicate how the carbon atoms of a given compound are bonded together in a characteristic lattice of chains and rings. The IUPAC Systematic Approach to NomenclatureĪ rational nomenclature system should do at least two things. Such common names often have their origin in the history of the science and the natural sources of specific compounds, but the relationship of these names to each other is arbitrary, and no rational or systematic principles underly their assignments. Just as each distinct compound has a unique molecular structure which can be designated by a structural formula, each compound must be given a characteristic and unique name.Īs organic chemistry grew and developed, many compounds were given trivial names, which are now commonly used and recognized. Rule #5- When there are 2 different side chains name them in alphabetical order using the carbon prefix (meth, eth.).The increasingly large number of organic compounds identified with each passing day, together with the fact that many of these compounds are isomers of other compounds, requires that a systematic nomenclature system be developed. You better have 3#'s when you have the tri prefix. Since we have 3, one carbon side chains, it is called "trimethyl". 3+3 always use the lowest numbers.Īgain, each side chain gets a number. (NOTE numbers and letters are separated by a hyphen)ĭid you notice we had to number from the right? If we named from the left it would be 3,3-dimethyl butane.Ģ+2 vs. You may have to number the longest chain from the right side to find the lowest number. Rule #4 When necessary use the lowest number to give the location of each side chain. WAIT.these are different structures with the same names. Rule #3- Multiple side chains will use prefixes 2 is di-, 3 is tri-, 4 is tetra- and so on.Ģ separate, one carbon side chains is dimethyl The longest chain is 3 carbons, so "propane". They are placed before the longest chain when naming. Rule #2- Remaining side chains will be given the ending -yl. Rule #1- Name the longest continuous chain of carbon atoms, and end it with -ane. Naming Compounds- Ignore all the hydrogen's. ![]() Makes for a good multiple choice question. The first 3 alkanes have no isomers (they can only be drawn 1 way). So let's look at the structural formulas and name each. You never really know how the molecule is constructed. Homologous Series- Did you notice that as you go down from CH 4 to C 2H 6 (and so on) the next member is different by 1 carbon and 2 hydrogen? The general formula is C nH 2n+2, n is the number of carbons is used to determine the number of hydrogen atoms. The rule for naming is they all end with "-ane". I am going to take you through all the isomers of methane through octane.Īlkanes- Are saturated (all single bonds) hydrocarbons (hydrogen and carbon only). If you just want the rules click here=> RULES. I found over the years that just giving the rules is overwhelming for naming organic compounds. ![]()
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