How Many Molecules Match the Given Structural Description?

[chloé]

bonjour ! voici un exercice que je n'ai pas réussi a faire lors de mon dernier contrôle... pourriez vous m'aider pour que je puisse comprendre pour la prochaine fois? je vous remercie beaucoup.

"compte tenu de la présence d'un carbone tétraèdrique et d'une double liaison particulière, expliquer combien de molécules sont conformes aux informations données par le nom fourni pour définir (incomplètement) cette molécule."

je ne sais pas si il faut utiliser les noms des molécules de l'exercice précédent...
si elles sont nécessaires, les voici :
3,5-diéthyl-4-isobutyl-6-méthylnonane
et 1,2-dibromo-3-chloro-5-éthylocta-1,4-diène

 

[Gokul43201]

Lisez ceci : https://www.physicsforums.com/showthread.php?t=28

Que pensez-vous?

 

[dextercioby]

That thread is locked.May i express my frustration for understanding the French,but not the organic chemistry?

Daniel.

 

[Gokul43201]

Dex, from what I understand, the question is asking for the number of conformational isomers. Is this correct ?

 

[dextercioby]

Nope,a mot-à-mot translation would b

Taking into account the presence of a tetrahedrical carbon (atom) and (the presence of a) double bond,explain how many molecules are conformal to the information given by their names in order to (incompletely (is this a typo?)) define the molecule"...

Daniel.

 

[Gokul43201]

I still think this is asking for the number of conformers (or conformational isomers), but perhaps I'm just not used to the way this is phrased.

The "incompletely" makes sense too. The type of conformer (cis-, trans- ,...) is not included in the name so as to permit all conformations.

Besides, the most important things to keep in mind when working with conformers are :
1) the tetrahedral geometry of sp3 hybrid C-atoms
2) double (and triple) bonds prevent rotation.

 

[iansmith]

Taking into account the presence of a tetrahedrical carbon (atom) and (the presence of a)double bond,explain how many molecules fit[/Color] the information given by their names and based on this information [/color](incompletely) define the molecule"...

Change conformal for Fit. It should make more sense.

 

[dextercioby]

I guess my English is a slacker.

Daniel.

 

[chloé]

hello !

I don't want you to do this exercice, bur just to help me (explanations).
In this exercice I have to explain how many molecules are in accordance with these informations: the carbon is "tétraedric" and there is a double connection.
the name of the molecule is 1,2-dibromo-3-chloro-5-éthylocta-1,4-diène

I hope you understand my translation...

 

[Gokul43201]

The first step is to draw the structure of the molecule.

How many carbon atoms in the main chain ?