Biology; Chemistry; Physics: Post your doubts here!

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Snowysangel

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Could someone please answer this. Why are alternate carbons bonded to ch3 groups in the structure of polypropene?
 
Saad Mughal

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Snowysangel said:
Could someone please answer this. Why are alternate carbons bonded to ch3 groups in the structure of polypropene?
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The CH3 or Methyl group is attached alternatively in many ways in the polymer, it affects the melting point and crystalline structure of the polymer.
If you are asking why, then consider the monomer, i.e. propene, it has a carbon-carbon double bond with 3 hydrogen atoms and a methyl group attached, when the polymer forms (by addition), there is a series of propene molecules that add up to each other, this forms a single horizontal carbon chain connected to hydrogen and methyl group alternatively. Here's a picture of how propene is drawn to form a polymer.
propene.png
 
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Snowysangel

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Saad Mughal said:
The CH3 or Methyl group is attached alternatively in many ways in the polymer, it affects the melting point and crystalline structure of the polymer.
If you are asking why, then consider the monomer, i.e. propene, it has a carbon-carbon double bond with 3 hydrogen atoms and a methyl group attached, when the polymer forms (by addition), there is a series of propene molecules that add up to each other, this forms a single horizontal carbon chain connected to hydrogen and methyl group alternatively. Here's a picture of how propene is drawn to form a polymer.
View attachment 26150
Click to expand...
What if there's no alkyl group attached to the monomer?
 
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Snowysangel said:
What if there's no alkyl group attached to the monomer?
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That's not possible for propene, the reason is that unless the monomer structure is like the picture I posted above, the polypropene CANNOT form since a repeat structure would not be formed.
 
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Snowysangel

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Saad Mughal said:
That's not possible for propene, the reason is that unless the monomer structure is like the picture I posted above, the polypropene CANNOT form since a repeat structure would not be formed.
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Does polymethene exist? So if the unsaturated hydrocarbon doesn't have an alkyl group, it can't have a repeat unit? What if the repeat unit is h-c-h-h-?
 
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Snowysangel said:
Does polymethene exist? So if the unsaturated hydrocarbon doesn't have an alkyl group, it can't have a repeat unit? What if the repeat unit is h-c-h-h-?
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Methene doesn't exist so how can Polymethene exist?
Unsaturated hydrocarbons from propene onwards need an alkyl group to form polymers.
The repeat unit, has to be the single molecule of the substance.
 
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hello ppl! if the questions asks us to state ohm's law, do we just right R=V/I? or r we supposed to explain something? (the question was for 2 marks for some reason) :s (IGCSE physics btw)
 
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Al-Anoud said:
hello ppl! if the questions asks us to state ohm's law, do we just right R=V/I? or r we supposed to explain something? (the question was for 2 marks for some reason) :s (IGCSE physics btw)
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Ohm's law states that at constant temperature and pressure, all ohmic conductors' voltage is directly propotional to the current (i.e. R=V/I), where R is the constant/resistance.
 
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