Leah here from leah4sci.com and in this video, I will show you how to name aldehydes. An aldehyde is a molecule that can be represented by R bound to a C, double bound to an Oxygen, single bound to a Hydrogen. Where R represents the rest of the molecule and the C double bound or single bound H represents the aldehyde. Be careful not to confuse the functional group on an aldehyde with that of a carboxylic acid which has an extra Oxygen. between the carbon and hydrogen and the ketone which has another R group attached rather than the hydrogen.
To name an aldehyde we use the rules explained in previous naming videos and apply the suffix Al. An interesting thing about the aldehyde is because it ends in an H it's a terminal functional group and when the aldehyde is the highest priority on your molecule it will always be considered number one and therefore you do not have to include a number. When drawing an aldehyde aligned structure, you can represent it with simply the carbonyl showing the carbon double bound to the oxygen. Some people will add a hydrogen, I prefer to draw it this way because it helps me recognize that it is indeed an aldehyde. We identify and highlight the parent chain and number to give the aldehyde number 1. In this case I have 2 carbons for a first name of F, only single bonds on the actual carbon chain giving me a last name of ane.
The aldehyde appears on carbon 1 which would give me 1-al but remember that 1 is understood and does not have to be included. Since the suffix ends in a vowel, we have to drop the E from ane for a final name of ethanol. When you have a substituted aldehyde, you treat it the same way.
We start by identifying and highlighting the parent chain and numbering to give the aldehyde number 1. On this molecule, I have 4 carbons for a first name of but. only single bonds on the chain giving me a last name of A. I have an aldehyde to give me the ending L and the methyl group on carbon 3 to give me the prefix 3-methyl. Putting the name together we start with the prefix, first name, last name and AL remembering to drop the E for a final name of 3-methylbutanol. When you have another group on your molecule that can potentially get the same number as your aldehyde, you can put the number of the You have a choice of giving the aldehyde a 1 or the pi bond a 1, however the aldehyde takes higher priority and so we number from the right.
Having 5 carbons in my parent chain gives me a first name of pent, a double bond on carbon 4 gives me a last name of 4-ene. The aldehyde gives me a suffix of al for a final name of 4-pentenal remembering that we dropped the e before placing the al suffix. When you have an aldehyde coming off of a cyclic compound, you name the cyclic compound and give it the ending carbaldehyde showing this is a carbon aldehyde. Since the cyclic compound has 6 carbons and no substituents, we simply call it cyclohexane. The aldehyde coming off the chain gives me an ending of carbaldehyde for a final name of cyclohexane carbaldehyde.
When you have a ridiculously substituted aldehyde, you treat it the same way by first highlighting and identifying your parent chain. Since only groups like a carboxylic acid will have higher priority than aldehyde, unless you see a carboxyl, aldehyde will be number one and everything else gets numbered accordingly. In this molecule, I have six carbons in my parent chain for a first name of hex, only single bonds gives me a last name of ain.
The aldehyde will give me a suffix of Al and I will carefully mark every substituents to ensure I don't miss one. Be careful that you don't confuse the isopropyl with the two methyl substituents and the way you can recognize the difference is to see that the isopropyl has a carbon coming off the parent chain whereas the methyls come directly off the parent chain. An isopropyl on the third carbon gives me three isopropyl. 2 methyls off the 5th carbon gives me 5,5-dimethyl and a benzene looking ring off the 6th carbon gives me 6-phenyl not 6-benzyl.
When ordering the substituents in alphabetical order, remember to look at I for isopropyl, the M for dimethyl since di simply means 2 and the P for phenyl. Since I comes before M which comes before P, the substituents are already in order. Remember to drop the E and ensure that you include each part of the puzzle for a final name of 3-isopropyl-5,5-dimethyl-6-phenylhexanal.
Here we have an interesting example. Given that the alcohol is not your highest priority, and therefore gets demoted from a functional group that ends in OL to a substituent with a prefix hydroxy. I start by identifying and highlighting my longest carbon chain and numbering to give the aldehyde number 1. 5 carbons gives me a first name of pent, only single bonds gives me a last name of ane.
My OH substituent on carbon 2 gives me the prefix 2-hydroxy and the methyl substituent on carbon 3 gives me the prefix 3-hydroxy. 3-methyl. And let's not forget the aldehyde giving me the suffix al. Since H comes before M, we get a final name of 2-hydroxy-3-methylpentanol remembering to drop the E before the al. We'll end off with an interesting example where a single carbonyl carbon has a hydrogen attached to either side.
You may recognize this molecule as having a common name of formaldehyde but let's see how to name it. While this may look like a di-al given that it's an aldehyde from either direction, we still start by identifying the one carbon in the parent chain for a first name of meth. Since there are no other bonds in the chain, this is by default an ane and the suffix is still al for the aldehyde, drop the e for a final name of methanol. Are you struggling with organic chemistry? Are you looking for information to guide you through the course and help you succeed?
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