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L O.

asked • 07/19/14

help with chemical formulas

how do I write the chemical formulas for:
 
 
   1.        H   H   H   H
         H   C   C   C   C    H
              H   H        H
                  H    C  H
                         H
 
 
2             H   H    H    H
       H      C   C    C    C       H
               H         H    H
                H   C      H
                     H
 
 
why would these substances be organic or hydrocarbons?
 
why would they be saturated or unsaturated?

1 Expert Answer

By:

Michael B. answered • 07/19/14

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5 (1)

Doctor Loves to Teach Computer, Statistics

L O.

I have them both showing C5H12  for their chemical formulas since they both have the same number of carbon and hydrogen atoms.
 
Since they only both have hydrogen and carbon atoms then they both would have to be hydrocarbon.
 
I am still stuck about if they would be organic.
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07/19/14

Michael B.

Good. Also, though it's a bit hard to tell from the diagrams without lines, it seems both molecules are the same, just drawn from opposite sides. Now you need to be sure that you haven't been learning formulas written like C3(CH2)4CH3. Those are called condensed formulas and show not only the total number of each atom in the molecule but how they're arranged. If the question refers to that kind of formula, then C5H12 would not be correct. 
 
Look up the definition of "organic" that you're using in your course, or check the Internet.
 
You still need to figure out if the compound is saturated or unsaturated, so that's another definition to check, and you'll need to look at the structure to see whether there are any double bonds.
 
 
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07/19/14

L O.

1.            H    H   H   H
                ι     ι     ι    ι
          H - C - C - C - C - H
                ι     ι          ι
               H    H    ι    H
                    H -  C - H
                           ι
                           H
 
 
2.       H   H       H    H
           ι    ι        ι     ι
       H-C - C -    C -  C- H
           ι    ι        ι      ι
          H    ι       H     H
           H- C   -   H
                ι
               H
 
These lines might not be perfect but does this help?
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07/19/14

Michael B.

Right, hat's what I figured. Look at the structure. There is a string of -CH2- capped with hydrogen at the ends, so a basic hydrocarbon chain (butane, in this case since it's 4 carbons long). But the second carbon in the chain is attached not to two hydrogens, but to one hydrogen and one methyl (CH3) group. Not that you necessarily need to know this, just that it might help to visualize the overall structure rather than just seeing a bunch of C's and H's. So overall, leaving out the hydrogens for simplicity, you have
 
         C
C-C-<
         C
 
Back to the question of saturated or not, ... are there any double bonds? Any carbons that don't already have 4 individual bonds? What does that mean re: saturation?
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07/19/14

Michael B.

Sorry, I left out one carbon. It should be 
 
            C
C-C-C-<
            C
 
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07/19/14

L O.

Okay so I am checking to see if I am on the right track. 
 
1.  the chemical formulas for both is C5H12.  We have not learned the condensed formula.
2.  they are hydrocarbons since they have the same number of hydrogen and carbon
3.  they are organic since these substances are consisting only of hydrogen and carbon
4.  they do no not have the same molecular structures because the frame work in the first structure does
     not connect but does connect in the second structure
5.  they are structural isomers because they have the same formula but different structures.  they have different physical and chemical properties.
6.  they are both unsaturated because the carbons are bonded to fewer than four atoms
 
thanks
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07/20/14

Michael B.

Very good. I'm impressed by your organized thinking and writing! Some clarifications:
 
  1. yes
  2. they're hydrocarbons but don't have the same number of hydrogen and carbon ... but they have only hydrogen and carbon. 
  3. organic doesn't mean that it contains only H & C -- that's what hydrocarbons are. Organic means, broadly, anything containing carbon, but there are are different specific definitions which is why I said you should check your own source for your class
  4. The way you have drawn the molecules at the top, I can't see how they are different. Both are branched one carbon from the end. They're both isopentane as shown on the Wikipedia page for that compound: http://en.wikipedia.org/wiki/Isopentane. Check your drawing and your assignment question. Or perhaps I'm still just not seeing the difference.
  5. yes
  6. The way I see the diagram, all the carbons are bonded to four atoms so there are no double bonds, so the compound is saturated. Again, I might be missing something. Which atom do you think has fewer than 4 bonds?
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07/20/14

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