An organic question

[dstormz]

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I'm still bewildered about the process of finding different hydrogens in a given structure?

For example, how many different hydrogens are there in 1-isopropyl-1-methylcyclopentane?

P.s. What is the name of this topic called? I can't find it in my orgo book 🙁


*Thank you so much for replying you guys 🙂

P.S. that illustration was very helpful bananaface. 😀

 

[bananaface]

You need to draw the structure and count them.

 

[jemc2000]

A reminder poem I use to remember the number of carbons is:

Mother's eat potatoes,
but papas ham,
however onions nobody digs

Meth-, eth-, prop-, but-, pent-, hex-, hept-, oct-, non-, dec-.

Then remember that each carbon has 4 bonds, so it is either connected to another carbon, or a hydrogen. (In simple alkanes).

But as bananaface states, drawing them is the best way. Don't forget to draw in the 2 hydrogens on each carbon in your cycloalkanes.

I just started Organic this semester but I am really enjoying it. Go ahead, call me a freak.

 

[dstormz]

You need to draw the structure and count them.

The thing is that i'm confused about counting the different hydrogens 🙁

 

[s13]

This is called Proton NMR (Nuclear Magnetic Resonance). In 1-isopropyl-1-methylcyclopentane, there are 5 different types of hydrogens.

1. 6H doublet
2. 1H septet
3. 3H singlet
4. 4H triplet
5. 4H quintet

(please let me know if i answered you're question)

 

[bananaface]

This is called Proton NMR (Nuclear Magnetic Resonance). In 1-isopropyl-1-methylcyclopentane, there are 5 different types of hydrogens.

1. 6H doublet
2. 1H septet
3. 3H singlet
4. 4H triplet
5. 4H quintet

(please let me know if i answered you're question)

I think we are talking about drawing basic structures here. 🙂 NMR is probably outside the scope of the question. We are wanting to count up the number of hydrogen molecules in 1-isopropyl-1-methylcyclopentane.

 

[gdk420]

I'm still bewildered about the process of finding different hydrogens in a given structure?

For example, how many different hydrogens are there in 1-isopropyl-1-methylcyclopentane?

P.s. What is the name of this topic called? I can't find it in my orgo book 🙁

Think symmetry. Hydrogens that are symmetrical are the same, things that are not are different hydrogens.

 

[jemc2000]

In a simple alkane like you named, just draw the structure. Then,

1. Write in the carbons
2. Go to each carbon and count the number of bonds on it. Don't forget to count the bonds between them even if it is written something like CH3CH2CH3
3. Then make sure each carbon has 4 bonds. Wherever there aren't additional halides attached, you attach a hydrogen.

Go to the top of page 4 of this concept from my instructor. Perhaps that illustration will help.
Dr. Gray's Concepts

All of his concepts I find very helpful

 

[dstormz]

I think we are talking about drawing basic structures here. 🙂 NMR is probably outside the scope of the question. We are wanting to count up the number of hydrogen molecules in 1-isopropyl-1-methylcyclopentane.

That's exactly my point 🙂

By the way, s13, how did you determine that molecule?

thank you everyone else for replying 🙂

P.s. that link is great, too, jemc2000.

I downloaded 90 lectures. I'm greedy, huh?


weeeeeeeeee!

 

[imperial frog]

So which is it? Were you asking about the total number of hydrogens or the total number of different hydrogens?

 

[dstormz]

So which is it? Were you asking about the total number of hydrogens or the total number of different hydrogens?

I'm asking about the total number of different hydrogens. Sorry, if my question wasn't very clear before. 🙂

 

[luv2BPharmD]

I may be misinterpreting your question, but after drawing out your chemical structure, I would look to see what type of carbon your hydrogen is attached to. Are they attached to a primary, secondary, or tertiary C? Then, I would classify my hydrogens based on that and count the total number of each type.

 

[imperial frog]

Still not clear on what you are asking because you say "different hydrogens" in the first post but then you agreed with bananface about finding just the total number of hydrogens and then you say you need to know the different hydrogens again. There's a difference in how you approach it because different and total are two different concepts that you cover in organic. I don't know how far you are in organic, but later on you will find out that not all hydrogens are equal.

If you just need to find the total number, draw it out and count them up. If you need to know the different hydrogens and you don't have access to a NMR you still need to draw it up and look for any CHx atom groups that are symmetrical...meaning that the groups of atoms for each possible bond are exactly the same.

For instance, in CH3-CH2-CH2-CH2-CH3, the 2 CH3s on the end are exactly the same meaning that attached to each one is a CH2-CH2-CH2-CH3 chain so the 6 Hs involved all have the same property. The same with the 2 CH2s at the 2nd and 4th C, both of those have the same CH3 on one side and CH2-CH2-CH3 attached on the other side...no difference in sidechains so no difference in the group. The middle CH2 doesn't have any other CH2 pair so those hydrogens are different. It's not like the 2nd and 4th CH2 because on either side of the middle one there's a CH2-CH3 chain which is different from the CH3 and CH2-CH2-CH3 chains on those.

Luv2B...that's not quite accurate because you can have carbons of the same degree but they might not be symmetrical. In my example above the middle 3 carbons are the same degree but the middle one isn't the same as the other 2.

 

[bananaface]

Still not clear on what you are asking because you say "different hydrogens" in the first post but then you agreed with bananface about finding just the total number of hydrogens and then you say you need to know the different hydrogens again.

I guess I just assumed we were talking about the overall number of hydrogen molecules on the structure, since I can't imagine anyone doing NMR at this point in the year. I agree that the question needs clarification.

 

[imperial frog]

Depends on what class he's in...we covered NMR in the first or second week of organic 2.

 

[bananaface]

This should answer either question.