Nomenclature of this compound?

[Caffine]

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Is this: 1-(1,2-dimethyl-4-butyne)-benzene or 3-methyl-4-phenyl-1-pentyne

 

[Rabolisk]

I would go with the second one, but what does this have to do with the MCAT?

 

[elusiveCHILD]

The second one since the formula for the aromatic ring is C5H5 ( one of the benezene's H is replaced by a substituent) if it was a benzene it would be C6H6.

 

[Rabolisk]

The second one since the formula for the aromatic ring is C5H5 ( one of the benezene's H is replaced by a substituent) if it was a benzene it would be C6H6.

...?

 

[Caffine]

I don't know. It was covered in my prep course. I saw it in my notes with no answer though.

 

[Isoprop]

IIRC, the alkyne has priority of the benzene ring. So the second answer is correct.

 

[Caffine]

IIRC, the alkyne has priority of the benzene ring. So the second answer is correct.

sorry i have a few questions and i dont know anyone to ask.

when would i name a benzene ring as the parent chain?

what if instead of a benzene for the above picture we had a phenol group, the phenol would take priority right?

also are regular benzene rings classified under alkanes in priority (both being lower than alkenes)?

finally, if we had a chain of 7 carbons attached to a benzene ring, would this compound be called heptylbenzene or phenylheptane?

 

[loveoforganic]

Chemsketch spits out (3-methylpent-4-yn-2-yl)benzene

 

[Isoprop]

sorry i have a few questions and i dont know anyone to ask.

when would i name a benzene ring as the parent chain?

what if instead of a benzene for the above picture we had a phenol group, the phenol would take priority right?

also are regular benzene rings classified under alkanes in priority (both being lower than alkenes)?

finally, if we had a chain of 7 carbons attached to a benzene ring, would this compound be called heptylbenzene or phenylheptane?

I'm not well versed in the nuances of IUPAC rules except with simple cases.

The very general rule is that for functional groups with heteroatoms, the oxygen trumps nitrogen and the more oxidized trumps the more reduced functional group. So COOH trumps aldehydes but alcohols trump enamines. Halogens are almost always substituents.

For unsaturation, things that can be geometric isomers take priority. So alkenes and cycloalkanes have priority over alkynes and benzene rings.

And sometimes all those rules go out the window because we go by (a) what's easier or (b) common names. So tetraphenylmethane has the alkane group with the highest priority.

Generally, IUPAC accepts both has the name of the compound but only has 1 "preferred" name. IUPAC names are more focused on making sure a name can only mean one compound and not the other way around.

Finally, I highly doubt the MCAT will try to test you on the nuances of naming this compound because there are multiple right answers and they don't expect you to have the IUPAC handbook memorized. For naming compounds, make sure the obvious functional group has priority and the longest chain is numbered to eliminate wrong answers.

 

[elusiveCHILD]

...?

If I'm not mistaking an aromatic ring will be considered benzene if it has the molecular formula of C6H6. However in the example above, there is a substituent in place of one of the H's therefore making the molecular formula C5H5 which will make the aromatic ring phenyl.