# alkanes

Fiathahel
Posers and Puzzles 10 Feb '04 15:47
1. Fiathahel
Artist in Drawing
10 Feb '04 15:47
How many different alkanes are there with n carbon atoms.

Alkane: a collection carbon atoms, with the property that a carbon atom is connected with at least one and up to four other carbon atoms and has no cykels.
2. 10 Feb '04 19:09
Originally posted by Fiathahel
How many different alkanes are there with n carbon atoms.

Alkane: a collection carbon atoms, with the property that a carbon atom is connected with at least one and up to four other carbon atoms and has no cykels.
According to Wikipedia (http://en.wikipedia.org/wiki/Alkane), the generic formula for acyclic alkanes is C(n)H(2n+2).

According to the definition, there can only be exactly one alkane (by definition) for each n, so I would conclude that the answer to your question is 1.

-Ray.
3. Fiathahel
Artist in Drawing
11 Feb '04 08:43
Originally posted by rgoudie
According to Wikipedia (http://en.wikipedia.org/wiki/Alkane), the generic formula for acyclic alkanes is C(n)H(2n+2).

According to the definition, there can only be exactly one alkane (by definition) for each n, so I would conclude that the answer to your question is 1.

-Ray.
I do no know what you mean with C(n)H(2n+2)

Their are more than one alkanes possible with n C-atoms. for example with n = 4:

C-C-C-C

and

C
|
C-C
|
C
4. Acolyte
11 Feb '04 11:241 edit
Originally posted by Fiathahel
I do no know what you mean with C(n)H(2n+2)

Their are more than one alkanes possible with n C-atoms. for example with n = 4:

C-C-C-C

and

C
|
C-C
|
C
Is

//////C///
//C///C///
C C C C C
//C///C///
//C///////

different from

//C///C///
C C C C C
//C///C///
//C///C///

? (The slashes are for spacing purposes)
5. Fiathahel
Artist in Drawing
11 Feb '04 12:52
Originally posted by Acolyte
Is

//////C///
//C///C///
C C C C C
//C///C///
//C///////

different from

//C///C///
C C C C C
//C///C///
//C///C///

? (The slashes are for spacing purposes)
No, that is the same.

It is difficult to draw them here, but If you mean that there are 4 C's in the 2nd column and 4 in the 4th it is also the same as

//C///C///
C C C C C C
//C///C///
//C///////

You should see them as a 3D object that can twist in every direction.
6. 11 Feb '04 19:04
Originally posted by Fiathahel
I do no know what you mean with C(n)H(2n+2)

Their are more than one alkanes possible with n C-atoms. for example with n = 4:

C-C-C-C

and

C
|
C-C
|
C
C subscript(n) H subscript(2n+2)

-Ray.
7. Acolyte
13 Feb '04 11:30
Originally posted by Fiathahel
No, that is the same.

It is difficult to draw them here, but If you mean that there are 4 C's in the 2nd column and 4 in the 4th it is also the same as

//C///C///
C C C C C C
//C///C///
//C///////

You should see them as a 3D object that can twist in every direction.
Ah, that makes things easier. It means you can see an n-alkane as a relation ~ on the set {1,...,n} with the following properties:

~ is symmetric and antireflexive

The 'edges' (x,y) where x~y form a tree connecting the whole set

Given any x, the number of y for which x~y is &lt;5

Two relations are equivalent iff they can be mapped to each other by permutation of the set.
8. 13 Feb '04 14:57
Originally posted by Fiathahel
You should see them as a 3D object that can twist in every direction.
although

- - - c - - - -
c c c c c c c c
- - - c - - - -
- - - c - - - -

is different from

- - c - - - -
c c c c c c c
- - c - - - -
- - c - - - -
- - c - - - -

9. Acolyte
14 Feb '04 01:12
Originally posted by iamatiger
although

- - - c - - - -
c c c c c c c c
- - - c - - - -
- - - c - - - -

is different from

- - c - - - -
c c c c c c c
- - c - - - -
- - c - - - -
- - c - - - -

Not in the light of Fiathahel's example. If you picture the molecule as balls connected by sticks, both the balls and the sticks can be twisted as much as you like.
10. Fiathahel
Artist in Drawing
16 Feb '04 11:47
Another example, to make sure you know whats possible:

c c c c c c c
- c - c - c -
- - c c c - -
- - - c - - -

is also allowed
11. richjohnson
TANSTAAFL
16 Feb '04 20:50
Originally posted by Acolyte
Not in the light of Fiathahel's example. If you picture the molecule as balls connected by sticks, both the balls and the sticks can be twisted as much as you like.
I don't think that's always true. Some molecules, known as &quot;chiral&quot; molecules or &quot;stereoisomers&quot; can have different properties than their mirror image.
(i.e.:
/////D
/////|
A---C---B
/////|
/////E

is different than:
/////E
/////|
A---C---B
/////|
/////D)
12. Acolyte
17 Feb '04 11:16
Originally posted by richjohnson
I don't think that's always true. Some molecules, known as "chiral" molecules or "stereoisomers" can have different properties than their mirror image.
(i.e.:
/////D
/////|
A---C---B
/////|
/////E

is different than:
/////E
/////|
A---C---B
/////|
/////D)
That's why I asked. I think for the purposes of this puzzle we are to ignore chirality.
13. 17 Feb '04 18:35
Originally posted by Acolyte
Not in the light of Fiathahel's example. If you picture the molecule as balls connected by sticks, both the balls and the sticks can be twisted as much as you like.
I think it's impssible to twist balls and sticks to make those two the same!
14. Fiathahel
Artist in Drawing
18 Feb '04 11:46
Originally posted by iamatiger
I think it's impssible to twist balls and sticks to make those two the same!
Those balls are very twisty. It doesn't matter where the sticks are connected with the ball, but only that they are connected.
15. Acolyte