Organic Chemistry question...

[AmazingGracePlayer]

I've been working on this question for hours, and still don't get it, someone please help:

Give the IUPAC name of a compound that:

1. is a constitutional isomer of nonane
2. contains 5 methyl groups
3. contains 2 methylene group
4. contains 1 methine group (methine C is the 2nd C on parent chain)
5. contains 1 quaternary C (quaternary C is the 4th C of the parent chain)

I've been trying to draw the structure too, but can't seem to work out that out either...

[Ericman197]

I don't know if it's possible. I tried drawing it out and I keep ending up with either 1 or 3 methylene groups. According to the rules you posted, your starter molecule is:

(2,4,4)-trimethylpent-2-ene

with one carbon left over

You can add a methyl onto the 2 or 4 methyls, but then you'd only have one methylene

You could form a cyclobutane group on the 4 carbon but then you'd have three methylenes, same for a cyclopropane group because where would you put the extra methyl? Or you could put it somewhere as a methine but then you'd have two methines.

I think you're just destined to get this problem wrong!

[Brim]

man...I wish i could help you but I took Organic Chem (two semesters) in 1999 and I changed majors twice after (ending up in architecture)!! hehe. This does take me back though.

[AmazingGracePlayer]

Originally Posted by Ericman197

I don't know if it's possible. I tried drawing it out and I keep ending up with either 1 or 3 methylene groups. According to the rules you posted, your starter molecule is:

(2,4,4)-trimethylpent-2-ene

with one carbon left over

You can add a methyl onto the 2 or 4 methyls, but then you'd only have one methylene

You could form a cyclobutane group on the 4 carbon but then you'd have three methylenes, same for a cyclopropane group because where would you put the extra methyl? Or you could put it somewhere as a methine but then you'd have two methines.

I think you're just destined to get this problem wrong!

I get everything you said except for one part... If I add a methyl group onto one of the two 4's methyls, don't I still have 2 methylene?

[username n/a]

The answer is 4.

[AmazingGracePlayer]

I got the answer, it's 2,4,4-trimethylhexane. =]

[Techmonkey]

ahh organic chem, brilliant.

when I heard about the fire in the channel tunnel, when they mentioned phenol all I could think about were delocalised pi-electrons.

[bassybill]

Originally Posted by AmazingGracePlayer

I got the answer, it's 2,4,4-trimethylhexane. =]

Thread revival, missed it first time around.

According to IUPAC rules, shouldn't that be 2,2,4-trimethylhexane? To keep the position of the substituents numbered as low as possible.

If I'm right, the wording in the original question...

4. contains 1 methine group (methine C is the 2nd C on parent chain)
5. contains 1 quaternary C (quaternary C is the 4th C of the parent chain)

... is really not quite correct. Or am I missing something here?

[bassybill]

Also, "methine group" is non-systematic usage in this example, which might be okay in some cases but seems a little out of place in a question about systematic nomenclature. A better alternative might be "tertiary carbon" and this would also fit in with the usage in the last line of the question.

EDIT That could explain why Ericman197 couldn't get this - it seems he might have (correctly) understood methine to mean a carbon with one double and two single bonds, as per systematic usage. BAD question.

[gold_member_321]

Uhhhh What?

[varunkapahi]

man! this reminds me of my 12th grade horrors. i am so glad i managed to pass my chem exams by doing well in inorganic chemistry