ATAR Notes: Forum
VCE Stuff => VCE Science => VCE Mathematics/Science/Technology => VCE Subjects + Help => VCE Chemistry => Topic started by: kenhung123 on April 30, 2010, 09:03:47 pm
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2 chloro, 2 methyl, 3 hexen-4-ol
OR
2 chloro, 2 methyl, 4,3 hexenol
OR
2 chloro, 2 methyl, 4 hex-3-enol
OR
2 chloro, 2 methyl, hex-3-en-4-ol
Is it wrong if I started counting the other side? 5 chloro, 5 methyl ...
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5-chloro-5-methylhex-3-en-3-ol
i think :P
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Safest option is definitely the third one you wrote, no ambiguity
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umm, aren't they all wrong?
the hydroxy and methyl/chloro are separated by a carbon, so it CAN'T be 2,3.
Anyway, rules as far as I know for priority are:
1. Functional groups (carboxyl>ester>hydroxyl>amine)
2. Bonds (double & tripple)
3. Alkyl halides (chloro/bromo/idio etc.)
4. Alkyl groups (methyl/ethyl etc.)
-Number carbons according to shortest distance to highest priority group/bond.
-Name molecule in alphabetical order, disregarding di/tri/tetra.
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from left to right cause functional groups r more important then bonds and halide groups :)
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If functional groups are more important doesn't it mean you count from right?
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OH is a functional group
Cl is an alkyl halide
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It's not exactly left to right, it's whatever combination of numbers is the least (eg. the least adding up)
And sorry, I was wrong, I was only thinking about the positions of the numbers (before the hex etc.)
I think it should be 2-chloro-2-methyl-hex-3-en-4-ol
But I'm not entirely sure now...
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5-chloro-5-methyl- hex-3-en-3-ol
now i'm unsure whether to name the stuff in front in alphabetical order if they belong to differnet catergories or to name them according to importance? can someone help me out :P
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umm, aren't they all wrong?
the hydroxy and methyl/chloro are separated by a carbon, so it CAN'T be 2,3.
Anyway, rules as far as I know for priority are:
1. Functional groups (carboxyl>ester>hydroxyl>amine)
2. Bonds (double & tripple)
3. Alkyl halides (chloro/bromo/idio etc.)
4. Alkyl groups (methyl/ethyl etc.)
-Number carbons according to shortest distance to highest priority group/bond.
-Name molecule in alphabetical order, disregarding di/tri/tetra.
Yea you are right. My alcohol naming was wrong. Fixed. Thanks alot that priority list helps a lot
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OH is a functional group
Cl is an alkyl halide
Im pretty sure Cl is a functional group part of haloalkanes
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It's definitely alphabetical order. This is from Wiki:
When compounds contain more than one functional group, the order of precedence determines which groups are named with prefix or suffix forms. The highest precedence group takes the suffix, with all others taking the prefix form. However, double and triple bonds only take suffix form (-en and -yn) and are used with other suffixes.
Prefixed substituents are ordered alphabetically (excluding any modifiers such as di-, tri-, etc.), e.g. chlorofluoromethane, not fluorochloromethane. If there are multiple functional groups of the same type, either prefixed or suffixed, the position numbers are ordered numerically (thus ethane-1,2-diol, not ethane-2,1-diol.) The N position indicator for amines and amides comes before "1", e.g. CH3CH(CH3)CH2NH(CH3) is N,2-dimethylpropanamine.
Edit: Maybe anna is right. I know the NEAP book puts alkyl groups ahead of alkyl halides.
e.g. it said methylcholoropentane, which is not in alphabetical order. it was something like that. but that is weird, as alkyl halides>alkyl groups.
this stuff is confusing!
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hold on carboxyl can't have numbers
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um i'm saying as in if u have
amine and floro or something and since amine is more important than floro u put it first when naming it?
what happens if it was ether and chloro
since in alhapbetical order it should be chloro ether blahahaha
but if we talk about its importance functional groups>halidealkyl groups do we name in ether chloro balahah regradless of the alpahbet? this is what i'm confused about d:
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carboxy is most important, so the suffix will always be like -oic. if there is a hydoxy group u dont call it alcohol its called .. hydroxy and if its amine, you call it amino as the prefix. all prefix are in alphabetical order, so u can have 1-amino-2-chloro-3,4-dimethybutanoic acid
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carboxy is most important, so the suffix will always be like -oic. if there is a hydoxy group u dont call it alcohol its called .. hydroxy and if its amine, you call it amino as the prefix. all prefix are in alphabetical order, so u can have 1-amino-2-chloro-3,4-dimethybutanoic acid
regardless of hirachy?
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Read this, it should help.
http://depts.uwc.edu/chemistry/helpful_files/nomenclature.pdf
And yeah, as carboxyl is the highest priority functional group, any molecule that contains it must end in the suffix 'oic acid'
A hydoxyl or amine group would be prefrixed as 'hydroxy' or 'amino'
If you have an amine as the highest prioirty functional group however, the suffix MUST be 'amine.'
You can't name it as an alkane or whatever and then put 'amino' as a prefix. VCAA will mark it wrong!
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Read this, it should help.
http://depts.uwc.edu/chemistry/helpful_files/nomenclature.pdf
And yeah, as carboxyl is the highest priority functional group, any molecule that contains it must end in the suffix 'oic acid'
A hydoxyl or amine group would be prefrixed as 'hydroxy' or 'amino'
If you have an amine as the highest prioirty functional group however, the suffix MUST be 'amine.'
You can't name it as an alkane or whatever and then put 'amino' as a prefix. VCAA will mark it wrong!
confused :( sorry
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Look at this:
http://vcenotes.com/forum/index.php/topic,25206.msg257152.html#msg257152
It's got the examiners report which explains what i'm saying.
Mao also gives a nice explanation. :)
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I don't really see functional groups as being prioritized over each other.
A carboxylic acid functional group can only be attached to the end of a carbon chain, hence it's logical that when naming the molecule you start counting from the carboxylic acid group, so that you avoid having to ascribe a number to the carboxylic acid group's position.
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^they are. if you had a hydroxy and an amino group in the same molecule, you would name it with the suffix 'ol' and not 'amine.'
And the hydroxy group could be anywhere on the molecule...
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Stonecold and annahinh are right
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The IUPAC basic principles show alkyl group>secondary functional>double bond and they do not mention alkyl halides at all...
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Thank you stonecold for linking. Here's the post.
For the sake of VCE, you'll always get fairly simple molecules to make, and it'll be pretty clear which ones are primary and which ones are secondary. So the rule simplifies to:
- Identify the functional group that will be assigned by the suffix
- Number the parent chain in a way to minimize the number of the above functional group
- All other functional groups will be assigned by prefixes, group in alphabetical order
Hence, carboxyl groups (COOH) will always be 1, and the hydroxyl group will always be minimized (for the sake of VCE)
In this case, -OH (hydroxy) takes precedence, it is the primary functional group. Secondary functional groups are chloro, methyl and alkene.
The name here will be 5-chloro-5-methylhex-3-en-3-ol. [Note the use of en, and the numbers are infixes. Between numbers and letters there should be a hyphen, and there are no spaces in a name (except for esters)]
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What exactly is the priority of secondary functional groups?
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What exactly is the priority of secondary functional groups?
It doesn't matter, numbering of the chain happens when you decide on the primary functional group, i.e. OH is numbered 3, thus alkene is also numbered 3.
But if you must know, after where this table ends, the order of precedence goes:
alkene > alkyne > halides > alkyl
Source:
http://commons.wikimedia.org/wiki/File:But-1-en-3-yne.svg - alkene precedence over alkyne
http://www.chemicalbook.com/ChemicalProductProperty_EN_CB4429957.htm - halide precedence over alkane
http://www.chemicalbook.com/ChemicalProductProperty_JP_CB51097071.htm - alkene precedence over halide
http://www.chemicalbook.com/ProductChemicalPropertiesCB7422328_EN.htm - alkyne precedence over halide
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Oh ok, thanks a lot Mao and Alkyl goes before alkane and after halides?
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The 'alkane' group I written there means alkyl groups, I should have been more clear. Alkanes chains (the longest parent chain) has no precedence since it does not require numbering.
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Doubt vcaa would get that hardcore about it.
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Okay, so I just want to be clear about naming amines.
WARNING! Heinemann book teaches it wrong. You can not name something aminoethane. It has to have amine in the suffix in it, so it is actually ethylamine/ethanamine.
What I would like to like confirmed is the following:
For propane with an amine group attached to carbon 1, the name is propylamine/propanamine
For propane with an amine group attached to carbon 2, the name is 2-propylamine/propyl-2-amine/2-propanamine/propan-2-amine
Is this correct?
Also trimethylamine is just a nitrogen with three methyl groups stuck onto each bond in place of a hydrogen yeah?
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Okay, so I just want to be clear about naming amines.
WARNING! Heinemann book teaches it wrong. You can not name something aminoethane. It has to have amine in the suffix in it, so it is actually ethylamine/ethanamine.
What I would like to like confirmed is the following:
For propane with an amine group attached to carbon 1, the name is propylamine/propanamine
For propane with an amine group attached to carbon 2, the name is 2-propylamine/propyl-2-amine/2-propanamine/propan-2-amine
Is this correct?
Also trimethylamine is just a nitrogen with three methyl groups stuck onto each bond in place of a hydrogen yeah?
r u sure D: about the amino thingo T^T
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Okay, so I just want to be clear about naming amines.
WARNING! Heinemann book teaches it wrong. You can not name something aminoethane. It has to have amine in the suffix in it, so it is actually ethylamine/ethanamine.
What I would like to like confirmed is the following:
For propane with an amine group attached to carbon 1, the name is propylamine/propanamine
For propane with an amine group attached to carbon 2, the name is 2-propylamine/propyl-2-amine/2-propanamine/propan-2-amine
Is this correct?
Also trimethylamine is just a nitrogen with three methyl groups stuck onto each bond in place of a hydrogen yeah?
r u sure D: about the amino thingo T^T
you cant name it amino unless theres a carboxy or alcohol thingy
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Yeah, certain Anna.
Take a look at 8bi.
http://www.vcaa.vic.edu.au/vcaa/vce/studies/chemistry/assessreports/2009/chemistry_assessrep_june09.pdf
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Yea the textbooks are pretty bad in that it does not clarify the priorities and that the highest priority is assigned the suffix. They seem allow prefixes and suffixes to be used interchangeably.
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The difference here is between 'naming' and 'systematic naming'. 2-Aminopropane or even hydroxyethane are perfectly valid names, but are not systematic names (2-propanamine and ethanol).
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Thanks for clearing that up Mao.
What is the systematic name for the following molecule?
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3-Chloro-6-methylheptane?
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Nah, that was the mistake I first made, but then I picked up on it.
I said it was 3-chloro-6-methylheptane. Which VCAA says is wrong. :(
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Thats what i thought it would be to. What do VCAA say?
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well this is from Checkpoints, so unless they stuffed it up, VCAA says:
5-chloro-2-methylheptane
I was under the impression that halogens were of a higher priority than alkyl groups...
Can anyone clarify. What if the chloro was attached to the second carbon from the left, and the methyl group attached to second carbon from the right. Then which end are you supposed to number from...
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Nah, that was the mistake I first made, but then I picked up on it.
I said it was 3-chloro-6-methylheptane. Which VCAA says is wrong. :(
Lol beaten. Anyway, I think halides>alkyl as it was confirmed by Mao.
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The exam report says the answer is:
Either of:
• 5–chloro–2–methylheptane
• 3–chloro–6–methylheptane.
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http://www.vcaa.vic.edu.au/vce/studies/chemistry/assessreports/2008/chemistry_assessrep_june08.pdf
We are all good people. Look at Question 6aii.
Both answers were accepted. Stupid Checkpoints only put one!
I was devastated when I thought I got that question wrong haha.
Also they didn't say one was right or wrong. It was a 50-50 split between students haha. So hopefully they wont give us something so ambiguous in this years paper, or at least they will accept all the reasonable answers.
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Well thats strange so treating halide=alkyl precedence is accepted..
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well this is from Checkpoints, so unless they stuffed it up, VCAA says:
5-chloro-2-methylheptane
I was under the impression that halogens were of a higher priority than alkyl groups...
Can anyone clarify. What if the chloro was attached to the second carbon from the left, and the methyl group attached to second carbon from the right. Then which end are you supposed to number from...
You number the positions of the functional groups and alkyl groups such that the total of the numbers in the systematic name is minimum.
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Err so whats the point of the priorities then?
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I think kyzoo is right, but VCAA doesn't really seem to mind on this one which is good.
Halogens are still greater priority than alkyl groups though.
Google:
2-chloro-4-methylpentane
4-chloro-2-methylpentane
Only the first one gives results. (This is a different molecule im talking about now btw, just in case of confusion)
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Umm, I think you number in such a way that the total number is least only when there is no functional groups. Which does not destroy the purpose of the priorities.