where does the n come from in a compound such as n-butane?
The n stands for "normal" meaning that the chain is a straight chain and not branched. I can't draw structures on the board but here is a site that will illustrate the difference between a straight chain and an isomer of that compound. Here is a site that shows a number of compounds but look at n-butane (a straight chain compound) and isobutane (a branched chain). They have the same formula of C4H10 but one has four carbons in a row and the other has only three carbon atoms in a row with the fourth one attached to the middle carbon.
http://www.geo.arizona.edu/xtal/nats101/9_16.jpg
The "n" in a compound name like "n-butane" stands for "normal." In organic chemistry, "n-" indicates that the carbon chain in the compound is linear or straight. It distinguishes it from branched isomers or cyclic compounds that have different structural arrangements.
To determine the name of a compound, such as n-butane, you need to follow the nomenclature rules established by the International Union of Pure and Applied Chemistry (IUPAC). In the case of butane, it is a hydrocarbon consisting of four carbon atoms in a straight chain. Each carbon atom is bonded to four hydrogen atoms.
To name it:
1. Start by identifying the longest continuous carbon chain, which in this case is four carbons long.
2. Assign the parent name based on the number of carbon atoms in the chain. In this case, it is "butane".
3. Add the prefix "n-" to indicate that it is a straight chain. If the chain were branched or cyclic, different prefixes or indicators would be needed.
4. If necessary, specify the positions of substituents or functional groups on the carbon chain using numbers. As butane has no substituents, it remains as "n-butane" without any numbers.
By following these steps, you can derive the name of the compound, including the "n" to indicate a straight carbon chain.