I have a few questions about OrgO. I think these are typos in the "Organic Chemistry as a Second Language 3rd Ed." book but I want to ask someone who would know. My bro (a chem major) and my sister (just matched) haven't been able to help. It'll probably require me to send pics of the problems so if anyone on FB or with text could help me I'd appreciate it, just PM me. Thanks! (Topics: nomenclature, resonance, etc)
OrgO Questions/1-on-1 Help
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5.27 parent is pent
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There are 2 lone pairs on oxygen so it's tetrahedral.
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4.19 should be bent geometry. Sp3 with 2 lone pairs is bent geometry
But the parent chain in 5.27 has to go through the double bond too, right? So isn't it prop?
And because one of the lone pairs is in resonance on the second problem, there's only one lone pair so it's bent, right?
And because one of the lone pairs is in resonance on the second problem, there's only one lone pair so it's bent, right?
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Well yeah, but I guess it depends which geometry the question is asking for. Electron-pair geometry or molecular geometry.
Electron pair geometry: tetrahedral
Molecular geometry: bent
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the parent chain will have to include the carbonyl carbon. the longest chain that includes that and the double bond is 5 carbons long. 2-propylpent-1-en-3-one
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5.27 - The longest chain including both functional groups is 5 carbons, with the ketone (being the more oxidized group) getting priority.
So I believe it would be named: 2-propylpent-1-en-3-one.
4.19 - Just gonna take an educated guess here: Oxygen, being allylic (one atom over from a pi bond) is primarily sp2 hybridized. The electrons in the pi bond can delocalize to the neighboring (left) oxygen via a network of available p-orbitals, resulting in a carbon with a slightly electropositive charge, and oxygen with a slightly electronegative charge.
EDIT 1: Sorry, you asked for geometry, not hybridization. I believe the geometry would be bent, like others said 😛 Although now I'm confused myself. How can an atom be sp2 hybridized and bent?
EDIT 2: I assumed since hybridization is involved, that only 1 lone pair was present + two other bonds were to atoms, for a total of 3 total groups (1 lone pair). This would lead to a bent shaped as well. Can anyone clarify if we should count the oxygen in the structure as having 1 lone pair or 2 when determining the geometry? It seems like the later line of thinking makes more sense, even though both result in bent geometry.
So I believe it would be named: 2-propylpent-1-en-3-one.
4.19 - Just gonna take an educated guess here: Oxygen, being allylic (one atom over from a pi bond) is primarily sp2 hybridized. The electrons in the pi bond can delocalize to the neighboring (left) oxygen via a network of available p-orbitals, resulting in a carbon with a slightly electropositive charge, and oxygen with a slightly electronegative charge.
EDIT 1: Sorry, you asked for geometry, not hybridization. I believe the geometry would be bent, like others said 😛 Although now I'm confused myself. How can an atom be sp2 hybridized and bent?
EDIT 2: I assumed since hybridization is involved, that only 1 lone pair was present + two other bonds were to atoms, for a total of 3 total groups (1 lone pair). This would lead to a bent shaped as well. Can anyone clarify if we should count the oxygen in the structure as having 1 lone pair or 2 when determining the geometry? It seems like the later line of thinking makes more sense, even though both result in bent geometry.
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Czar--you want the lowest numbers though.
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Haha, thanks for the heads up 😛 I think it's corrected now.
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The ketone and the alkene.
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while alkenes are not typically thought of as functional groups, you still should think of it as so when naming a compound (i.e. you want lowest number so if an alkene is between C1 and C2, that should be the numbering).
also be able to recognize lactones and lactams
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FYI, you can use use [.IMG][./IMG] tags, put link in between and remove periods.
For 5.27, you have a 7 carbon chain = heptane, but you need to include both the alkene and ketone.. so really we have a 5 carbon chain = pentane.
alkene at position 1 takes precedence over ketone at what would be position 3
propyl chain at position 2
therefore we have 2-propylpent-1-en-3-one. (note one poster had 3-propyl earlier but that is a typo I think).
always look for the LONGEST carbon chain that includes all functional groups (not necessarily ending on those functional groups.. longest is the goal).
for 4.19: the geometry of the bond on the right would be of the format AB2E2 (as in, two atoms connected, two lone pairs). This is bent.
also note that it is indeed sp3 hybridized since it does not donate electrons to the pi system to its right.
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think where the pi bond is moving.. it's not involving the electrons of the oxygen at all.
EDIT: well now that I think about it.. it could resonate with that system but it would be a very weak contributor to overall structure.. probably won't be asked one like this but I'd still consider it sp3
If we assume (I know, I know) the only functional groups to be considered in the first problem are these, then why does the parent group not go through the left double bond? Or does it?
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the parent group starts at the bottom of the double bond and goes up to the right, passing the ketone..
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because the alkene functional group would result in lower numbers being used which is favored (i.e. the alkene starts closer to an end).
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I have no clue what you are talking about now.
There is one alkene. There is one ketone.
We need to make a parent chain that involves both the alkene and the ketone.
We need to start numbering from the side that will hit either the alkene or the ketone first.
EDIT: maybe you think we need to go through the double bond of the ketone? we don't.. we're looking for the longest carbon chain here
C-1 is the bottom most carbon. C-5 is the right most carbon.
What is the parent chain if we only consider the following types of functional groups: carboxylic acid, ester, aldehyde, ketone, alcohol, and amine? For the sake of argument, please apply the regular rules of nomenclature but ignore alkenes as a functional group (since I don't think they'd ask me to answer based on something I haven't learned yet; I think they're not considering alkenes functional groups here). I'm not suggesting the functional group goes through the double bond in the ketone; I'm suggesting it goes through other double bond.
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You can't just ignore the the alkene and follow the other rules.. that's like asking someone to use PERAMDAS (or whatever) to solve a problem but then telling them to disregard multiplication. You're not using PERAMDAS if you disregard multiplication.. you're not using the nomenclature rules properly if you aren't using alkenes.
Alkenes are functional groups.. there's no way around that.
It won't go through the other double bond because that's an oxygen and we're looking for the longest CARBON chain. If you want to just pretend the alkene group doesn't exist and is an alkane instead, the longest chain would be a heptane going from RIGHT to LEFT with a ketone and methyl group attached.
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Just has to include the ketone (and other functional groups)..
by the way, ketone means the carbon double bonded to the oxygen.. it's the entire thing. Not just the oxygen. There's no such thing as a carbon under the ketone.. that IS the ketone.
So the parent string can go straight through from the R to the R' as shown below?
http://imageshack.us/a/img832/3681/3r3.png
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It WILL go through like that every single time
You are looking for the longest possible carbon chain. That means not stopping in the middle of a carbon chain EVER. For instance, the compound shown below in that image has a three carbon parent chain with a ketone at its C-2 position.
The book left nothing out. This nomenclature is typically assumed in orgo and is probably more suited for a general chemistry textbook.
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Again, this nomenclature is general chemistry stuff. You're supposed to know this going into organic chemistry like the back of your hand.
Ok, apparently you're a Klein fanboy... If he expected you to know it, he shouldn't be covering it. If he decides to cover it, he shouldn't leave out key info necessary to solve the problems. Maybe it's just in a different section of the book...
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I strongly disagree. Learned 0 naming in chemistry. Learned it all in organic.
Yeah, he only covered groups containing oxygen. Must be in another section I haven't gotten to yet. Good to know that a parent chain can pass "through" a ketone though. Explains a lot. Thanks guys!
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don't even know what book you're talking about or who Klein is. this would be similar to a book on calculus first covering addition though. Do you really expect that to happen?
you're asking for help on a topic that is so fundamental to chemistry in general and then have been unwilling to actually sit there and read what I and others have posted because it doesn't fit your interpretation of the book.
@ashtern, I've never seen a general chemistry course that did not basic nomenclature.. I'm talking about being able to identify the longest carbon chain here. Nothing past that.
not sure why quotation marks are being used here..
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It's so nice taking the time out of one's day to help someone and then get a thanks like this
good luck reviewing the rest of Orgo. If I were you, I'd take a step back and learn nomenclature the right way (not through a review book) because it's not something you want to piece together as you go.
Wikipedia actually provides a nice thorough outline of what to do:
http://en.wikipedia.org/wiki/IUPAC_nomenclature_of_organic_chemistry#Basic_principles
