Chemical Forums
Chemistry Forums for Students => High School Chemistry Forum => Topic started by: kensher on July 27, 2016, 08:28:44 AM
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Hello.
I got this one task in my text book where I am supposed to name the alcohol from carboxylic acid from an ester mixed with water.
Ester + water ::equil:: carboxylic acid + alcohol
In the task, we are only given the structural formula of the ester, not the name. The structural formula of the ester is:
CH3COOCH(CH3)2
The acid part is pretty easy to figure out – Acetic acid. The alcohol part is what I don't understand. I've drawn the problem as I understand it (see attachment).
If I am suppose to name the alcohol based on my drawing, it would be something like: 1-methyl-1-ethanol, which is obviously wrong (according to the text book and Google).
Would really appreciate if somebody could help me out.
I'm very greatful for all the help I have received on this forum. It really is invaluable ☺
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How many carbon atoms does the alcohol have?
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3, but one of them is a sidegroup (I think)?
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but one of them is a sidegroup (I think)?
No. Do you know how to count the longest carbon chain in the molecule?
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but one of them is a sidegroup (I think)?
No. Do you know how to count the longest carbon chain in the molecule?
Maybe not.
I would think that the C-atom which is bonded to the OH-atom becomes the longest chain and gets the number 1 like the picture below (see new attachment).
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Try re-numbering the carbon chain in a linear fashion.
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Try re-numbering the carbon chain in a linear fashion.
I don't know how. I can't figure out a way where I logically can count them in a linear fashion.
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Try from the top->down->right. You see how they can be connected linearly? In a fashion, it is the OH that sticks out from the middle. Can you turn the molecule around in your head to see that?
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Try from the top->down->right. You see how they can be connected linearly? In a fashion, it is the OH that sticks out from the middle. Can you turn the molecule around in your head to see that?
I guess you mean this (see attachment below)?
The name would then be 2-propanol.
But I still don't get why you are allowed to do this, because – like I said earlier – it looks to me like a methyl side group from ethane. I accept that this is wrong, but can somebody explain why it's not a sidegroup (how you can see it from the structural formula)?
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The problem may arise because in this thread http://www.chemicalforums.com/index.php?topic=86916.0 the OH group was not directly attached to the longest carbon chain. The alcohol is named based on the longest chain bearing the OH group. However, there is no requirement that the C atom bearing the OH should be the terminal carbon of the chain. Here you have a 3-carbon chain with an OH on the middle carbon. How would you name that?
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The problem may arise because in this thread http://www.chemicalforums.com/index.php?topic=86916.0 the OH group was not directly attached to the longest carbon chain. The alcohol is named based on the longest chain bearing the OH group. However, there is no requirement that the C atom bearing the OH should be the terminal carbon of the chain. Here you have a 3-carbon chain with an OH on the middle carbon. How would you name that?
Thanks for you thorough answer. Here is what I don't understand:
Let's just for the sake of simplicity forget the alcohol. When you have an CH3 coming out of an CH, and another one being alligned with the CH, I thought you had one main group (longest chain) of CH-CH3 and one sidegroup (CH3). Like the picture below.
The structural formula of the picture looks to me like 1-methylethane and not propane. I think that is what I don't understand.
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An example from my text book:
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1-methylethane and not propane
Rule - longest chain - propane is correct
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1-methylethane and not propane
Rule - longest chain - propane is correct
I appreciate you taking time to answer, but the answer was not very clarifying.
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Just read and memorize IUPAC rules
eg
http://chemwiki.ucdavis.edu/Core/Organic_Chemistry/Alcohols/Nomenclature_of_Alcohols/Naming_Alcohols
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Finally got it!
It all made sense when I realized I could change the place of the CH3 and the OH.
Thanks to everyone who submitted an answer ☺
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Longest carbon chain may be folded on paper on any manner, in fact it is always folded (tetrahedral angle).
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The structural formula of the picture looks to me like 1-methylethane and not propane. I think that is what I don't understand.
The molecule in your drawing is unbranched.