In IUPAC nomenclature you want to assign the highest priority functional group the lowest number possible in the carbon chain.ģ) Butyl 2-methylhex-6-enoate is wrong for a mix of the reasons in the previous 2 answers.
The "en" indicates there is an alkene (double bond) in the compound, and since there isn't this can't be the right answer.Ģ) Butyl 2-methylhex-6-anoate is wrong because the ester group isn't assigned the highest priority. Now let's go over the other answer choices and why they are wrong:ġ) Butyl 5-methylhexenoate is almost correct except for the fact it says Butyl 5-methylhex enoate. This makes our final answer Butyl 5-methylhexanoate. Since this chain has 4 carbons it is a butyl group, as according to IUPAC the chain on the side farthest from carbonyl carbon of the ester is named as a substituent and placed in front of the name of the compound. Let's first count the number of carbons it has. However, we aren't done as we haven't named the substituent on the other side of the ester. We also have a methyl group at the 5-carbon so in this gives us: Now that we have numbered the carbon chain we can begin our naming.Īccording to IUPAC convention the base name for an ester compound is -oate, so in this case we have a hexanoate, which can also be written as hexan-1-oate, but this isn't needed as it as the ester is at carbon 1. The reason why is because there are two possible pathways for the carbon numbering to continue, but both are equivalent meaning no matter what we do there is a 5-methyl group and the carbon chain is 6 carbons long. In this case this means we want the carbonyl of the ester to be carbon number #1, so let's start there and number the carbon chain. Next, we want to number the longest carbon chain with the highest priority functional group with the lowest number. Next, we should identify what functional group has the highest priority, as that will form the base name of the compound:Īccording to IUPAC convention, Carboxylic Acid derivatives including Esters have the highest priority then carbonyls then alcohols, amines, alkenes, alkynes, and alkanes, so in this case the Ester group has the highest priority and therefore makes up the name of the base compound. When naming an organic compound by the IUPAC rules, it's best to first start by identifying the functional groups present.
Because the higher priority groups are across the double bond from each other, the molecule is given the "E" designation. On carbon, the bromine is of higher priority than the methyl group (when taking atomic number into account, per the Cahn-Ingold-Prelog rules), and is located " above" the double bond. On carbon, the chlorine group is higher priority, and is located " below" the double bond. IUPAC rules state that the substituents are listed in alphabetical order when naming (thus " ").įinally, stereochemistry must be taken into account. " The substituents are a bromine on carbon and a chlorine on carbon. Counting from left to right puts the double bond between carbons and, which is lower than counting from right to left, therefore the numbering goes from left to right, and the molecule is thus a ". The highest priority functional group is the double bond, and the carbon chain must be numbered such that this functional group is given the lowest number carbon. The longest carbon chain is carbons long (thus " "), and the double bond makes it an alkene (thus " ").
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