Bond-line notation is a useful shorthand to draw and read complicated organic molecules easily. This article focuses on drawing a bond-line notation diagram (or skeletal structure) from an IUPAC name. This guide is intended for users with basic chemistry knowledge and is not written to be the sole source of instruction for this topic.
Steps
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Look at the molecule example that you have to reduce to bond line notation. (Note: bond-line notation and skeletal structure refer to the same thing.)
- Normally you will be given an IUPAC name instead of a formula, you may want to look at How to Name a Hydrocarbon Chain Using the IUPAC Method to help you.
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Consider the name. It will be made up of a few snippets of words (think "bromo", "hexa", "ane", "cyclo", and others) and some numbers. The numbers denote the location of the atom or functional group. Sometimes this will be followed by a name, for example 2-bromo (Bromine off Carbon 2) but sometimes not, for example 3-pentone, "pentone" being the name describing the main organic chain of the compound. The "one" means there is a Ketone, but the "pent" is talking about the general structure, saying it has 5 Carbons total. You would not say "3-ketone pentane".Advertisement
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Count the number of Carbon atoms. This will be denoted by using the prefix on the name of the chemical, see the list below. If the first 5 letters are "cyclo," this means the structure is polygonal in nature, we will cover this more in step 5.
- 1 carbon: Meth
- 2 carbons: Eth
- 3 carbons: Prop
- 4 carbons: But
- 5 carbons: Pent
- 6 carbons: Hex
- 7 carbons: Hept
- 8 carbons: Oct
- 9 carbons: Non
- 10 carbons: Dec
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Look at the main word of the compound name. For example, if you have 1-bromo 2,3 pentene (all the alkenes with chemical formula C5H10), look at the "pentene". If the first five letters of that word are "cyclo" then you have a compound that is polygonal in nature. the prefix after the "cyclo" tells you how many carbons, and by extension what shape you have. For example, "cyclohexane" is a polygonal structure with 6 carbons making up the ring, meaning it is a hexagon. If you see the word "Benzene" then you have a special polygonal structure . "Benzene" is the word that refers to a hexagon with alternating single and double bonds, it has the formula C6H6.
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If there is no "cyclo" or "benzene" in your name, draw a zigzag on your paper. You are drawing the bonds between the carbon atoms, with an atom residing at each end of the line segments you have drawn. If there are any non-carbon atoms making up the chain, do not denote them yet.
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Add any double or triple bonds. This is done by drawing a line above or beneath the specified line segment. Skip this step if your structures name ends with "ane."
- If your structure has a double bond, the last three letters of the main word will be "ene." The structure will also have two consecutive numbers with a comma separating them before the main name, for example 2,3-Hexene. The "2,3" means the double bond is between the second and third carbon.
- The procedure is the same for a triple bond, except the last three letters to look for are "yne." For example 2,3-Hexyne would mean a 6 carbon molecule with a triple bond between carbons 2 and 3.
- If you have a triple bond in your molecule, make sure to draw the functional groups on either side coming off at a 180 degree angle.
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Add any inorganic atoms to the chain. Do this by either erasing the apex and drawing the atomic symbol (see the N between carbons 3 and 4 as an example) or by adding in an additional bond line and writing the symbol at the end of it. Note that the carbons in the backbone of the molecule are indirectly labelled as apexes and ends of lines. Hydrogens off of these carbons are not denoted at all, but rather implied. Any hydrogens contained in functional groups are usually written, for example NH2, OH, COOH, and others.Advertisement
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QuestionIn bond line is more preference given to double or triple bond while numbering?HanCommunity AnswerWhen a choice remains, preference is giving to double bonds when numbering, according to the IUPAC's Blue Book.
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Tips
- Sometimes, if you have multiple groups coming off of a ring structure, some take priority over the others. This is done by automatically assigning the carbon containing these groups as carbon 1. For example, if you have 3-bromo benzoic acid, the "acid" portion (or COOH group) is automatically off of carbon 1, which can be arbitrarily assigned in a ring structure (because the ring structure is the same everywhere). The structure is correct if the bromine is 2 carbons over from the acid group.Thanks
- Sometimes there are carbon groups coming off of the main structure. One carbon is called a "methyl group," two is an "ethyl group" and so on. It is rare to have anything more than an ethyl group because naming conventions dictate finding whatever chain has the most carbons (this practice typically leaves only one or two carbons off the main chain).Thanks
- If you have an aldehyde, it will be denoted with the suffix "al," for example "Butyraldehyde". However, benzene with an aldehyde group is not "benzenal (an important organic chemical compound with the chemical formula C6H6)" but rather "benzaldehyde".Thanks
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