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Materials Science C

Posted: February 8th, 2018, 6:31 am
by Tesel
I was surprised to see that there wasn't a forum for this, so I'll start us off.

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A. Give the common name of this compound.

B. Give the strict IUPAC system name of this compound. (Even though the common name is also generally accepted by the IUPAC.)

Re: Materials Science C

Posted: February 13th, 2018, 10:31 pm
by wethose
A) tert-butylcyclohexane
b) (1,1-dimethylethyl) cyclohexane
Speaking in terms of hybridization, why do alkanes lack isomers?

Re: Materials Science C

Posted: February 14th, 2018, 6:47 am
by Tesel
A) tert-butylcyclohexane
b) (1,1-dimethylethyl) cyclohexane
Speaking in terms of hybridization, why do alkanes lack isomers?
Correct on both parts!

Alkanes have structural isomers, of course. However, they do not have geometric isomers. This is because they contain only sigma bonds, which are able to freely rotate between all possible geometric configurations. In terms of hybridization, their carbons form bonds with 4 sp3 hybrid orbitals. Geometric isomers occur when pi bonds (in double and triple bonds) restrict rotation around the sigma bond. To form such geometric isomers, carbon atoms must contain sp or sp2 hybrid orbitals for sigma bonds and p orbitals for pi bonds.

I assume this covers the question, but I will wait for you to verify before I post another question.

Re: Materials Science C

Posted: February 15th, 2018, 1:02 am
by wethose
A) tert-butylcyclohexane
b) (1,1-dimethylethyl) cyclohexane
Speaking in terms of hybridization, why do alkanes lack isomers?
Correct on both parts!

Alkanes have structural isomers, of course. However, they do not have geometric isomers. This is because they contain only sigma bonds, which are able to freely rotate between all possible geometric configurations. In terms of hybridization, their carbons form bonds with 4 sp3 hybrid orbitals. Geometric isomers occur when pi bonds (in double and triple bonds) restrict rotation around the sigma bond. To form such geometric isomers, carbon atoms must contain sp or sp2 hybrid orbitals for sigma bonds and p orbitals for pi bonds.

I assume this covers the question, but I will wait for you to verify before I post another question.
Yep! Thanks for catching the structural vs geometric thing.. I'm new to this event lol

Re: Materials Science C

Posted: February 15th, 2018, 4:52 am
by Tesel
Yep! Thanks for catching the structural vs geometric thing.. I'm new to this event lol
Not a problem, it was still a good question!

Below is a stress-strain curve characteristic of thermoplastic polymers:

Image

Given that this graph uses engineering stress and strain values, why does the polymer show a rapid decrease in stress after the yield strength, then a plateau, then a gradual increase in stress before fracture?

Re: Materials Science C

Posted: February 25th, 2018, 10:04 am
by IcsTam
Yep! Thanks for catching the structural vs geometric thing.. I'm new to this event lol
Not a problem, it was still a good question!

Below is a stress-strain curve characteristic of thermoplastic polymers:

Image

Given that this graph uses engineering stress and strain values, why does the polymer show a rapid decrease in stress after the yield strength, then a plateau, then a gradual increase in stress before fracture?
The polymer chains become increasingly oriented with the tensile axis, increasing the strength of the polymer (strain hardening)

Re: Materials Science C

Posted: February 25th, 2018, 11:54 am
by Tesel
The polymer chains become increasingly oriented with the tensile axis, increasing the strength of the polymer (strain hardening)
Correct!

Re: Materials Science C

Posted: February 25th, 2018, 4:27 pm
by IcsTam
What is the Ziegler-Natta catalyst and what is its function?

Re: Materials Science C

Posted: February 25th, 2018, 5:17 pm
by Name
What is the Ziegler-Natta catalyst and what is its function?
Ziegler natta catalyst is used in addition polymerization in order to control tacicity and eliminate branching, allowing to produce certain types of polymers that couldn't have produced otherwise

Re: Materials Science C

Posted: February 25th, 2018, 5:52 pm
by IcsTam
What is the Ziegler-Natta catalyst and what is its function?
Ziegler natta catalyst is used in addition polymerization in order to control tacicity and eliminate branching, allowing to produce certain types of polymers that couldn't have produced otherwise
Correct! Your turn.