How do I draw 5-methyl-3-ethyl-2-methylheptane?

Question

I think this may be a trick question.

It doesn't look like the name is written properly.  I think it should be 3-ethyl, 2,5-methylheptane.  Either way, how do I draw it?

 

If it was 3-ethyl, 2,5-methylheptane, I would draw the 7-link carbon structure, then add methyl groups off of 2 and 5, then draw an ethyl group off of 3.

Answer 1

From your question I take that you know how to interpret organic nomenclature so I will leave that alone. 

 

While the name may not be correct according to the IUPAC standards it still serves its purpose. When I took organic chemistry I would notice these incorrectly named compounds all the time, but similarly to the English language and the slang we speak to each other compounds can have many different incorrect names.

 

The actual correct name is 3-ethyl-2 5-dimethylheptane

 

REMEMBER...

 

1) always look so see what is the longest chain

 

2) look for repeated substituaents (like the two methyl's in this molecule resulting in the di)

 

3) start your name in alphabetical order while disreguarding prefixes (di, tri, tetra, penta...)

 

4) POINT THIS OUT TO THE PROFESSOR SO HE CAN CHANGE THIS !!! He should he teaching you the correct way to name and draw compounds.

 

You can see the compound your looking for here...

 

http://www.departments.bucknell.edu/chemistry/courses/chem211/problem_sets/naming_alkanes_ans.pdf

Answer 2

make a chain of 7 C's.  Add the groups according to the name.  Your name is correct.  If there are 2 methyl groups they are grouped as you had them and the substituents are listed alphabetically.

             C₂H₅  CH₃

             |        |

   C- C- C- C- C- C- C

        |  

        CH₃

Fill in the rest of the H's.  Notice it doesn't matter which direction or if you start with the "methyl" I drew down or the C I didn't give H's to, the name is the same.