Mod 7 (1 Viewer)

[=)(=]

Why are tertiary amines more basic than primary amines?

 

[wizzkids]

Yes, there are differences in the pH (or pKa) of aqueous solutions of the various amines, but the difference is not strong.
Here is some data for a series of amines:
methylamine (primary) pKa = 10.64
dimethylamine (secondary) pKa = 10.71
trimetylamine (tertiary) pKa = 9.77
As you can see, the most basic of these is dimethylamine, and the least basic is trimethylamine.

A more interesting question, and one that you should cover in the HSC Chemistry syllabus, is why are amines all bases, and yet amides are practically neutral in aqueous solution? The oxygen bonded to the amide functional group clearly makes a big difference to the reactivity of the non-bonding electron pair on the nitrogen.

 

[synthesisFR]

A more interesting question, and one that you should cover in the HSC Chemistry syllabus, is why are amines all bases, and yet amides are practically neutral in aqueous solution? The oxygen bonded to the amide functional group obviously make a big difference to the reactivity of the non-bonding electron pair on the nitrogen.

Is it because electron density is pulled from the nitrogen?
Also a similar argument for alcohols and carboxylic acids acidities right?

 

[wizzkids]

Is it because electron density is pulled from the nitrogen?

Yes, that is what we believe. The negative charge density of the non-bonding electron pair at the nitrogen is strongest when the adjacent carbon is bonded to carbon or hydrogen (the electronegativity of C and H is about 2). When oxygen (electronegativity of 3.44) fills a double bond on the adjacent carbon, it distorts the electron cloud towards the oxygen and away from the nitrogen making it less attractive.

 

[=)(=]

Thanks for the help, I also had a question regarding the loss of water for condensation polymerisation, how would u know if the loss is 2n-1 of n-1 cause like e.g for polyester two functional groups on either side, results in the loss of 2 waters when it reacts however in hsc answers they usually state it as n-1, so i am a bit loss tbh

n=units of monomers

 

[synthesisFR]

Thanks for the help, I also had a question regarding the loss of water for condensation polymerisation, how would u know if the loss is 2n-1 of n-1 cause like e.g for polyester two functional groups on either side, results in the loss of 2 waters when it reacts however in hsc answers they usually state it as n-1, so i am a bit loss tbh

Yeah so
If it’s something like lactic acid I think making a polymer or glucose riight
It’s only one monomer that’s used with two different functional groups on the ends
Then it’s n-1 water molecules formed

however if it’s a copolymer so made of two different monomers that have the same functional groups on either end
Then it’s 2n-1
So PET or nylon 6,6
For one repeat unit u need two of these diff monomers
I have a diagram in my notes that I drew that could be useful to help u understand I can send it tmrw cuz I’m in bed rn

 

[synthesisFR]

Ps I doubt anyone needs to know that tbh

 

[=)(=]

ahh ngl thats a pretty good explanation thanks brah

 

[=)(=]

Yeah so
If it’s something like lactic acid I think making a polymer or glucose riight
It’s only one monomer that’s used with two different functional groups on the ends
Then it’s n-1 water molecules formed

however if it’s a copolymer so made of two different monomers that have the same functional groups on either end
Then it’s 2n-1
So PET or nylon 6,6
For one repeat unit u need two of these diff monomers
I have a diagram in my notes that I drew that could be useful to help u understand I can send it tmrw cuz I’m in bed rn

wait kinda curious what is the reason behind the difference, cause i tried deeping it and either way the first polymerisation results in the formation of one water and subsequent polymerisatins result in 2 waters for both cases?

 

[synthesisFR]

wait kinda curious what is the reason behind the difference, cause i tried deeping it and either way the first polymerisation results in the formation of one water and subsequent polymerisatins result in 2 waters for both cases?

sorry i missed this



So basically if u look at the first image. Lactic acid has both groups on either ends so when it polymerises it loses one water overall after n molecules bc the there remains an O and a OH on either end.
For PET u can visualise it in two steps. For the second image ur effectively making a comonomer first, then this co monomer reacts with other ones to form n-1 H2O as it now has both groups on either end. if u add the two eqn u get (2n-1) water
was that ur question?

 

[nsw..wollongong]

sorry i missed this

View attachment 39138
View attachment 39139
So basically if u look at the first image. Lactic acid has both groups on either ends so when it polymerises it loses one water overall after n molecules bc the there remains an O and a OH on either end.
For PET u can visualise it in two steps. For the second image ur effectively making a comonomer first, then this co monomer reacts with other ones to form n-1 H2O as it now has both groups on either end. if u add the two eqn u get (2n-1) water
was that ur question?

why is your handwriting so neat

 

[synthesisFR]

why is your handwriting so neat

Is this sarcasm it’s so messy there lol

 

[nsw..wollongong]

Is this sarcasm it’s so messy there lol

stfu it looks like a font

 

[=)(=]

sorry i missed this

View attachment 39138
View attachment 39139
So basically if u look at the first image. Lactic acid has both groups on either ends so when it polymerises it loses one water overall after n molecules bc the there remains an O and a OH on either end.
For PET u can visualise it in two steps. For the second image ur effectively making a comonomer first, then this co monomer reacts with other ones to form n-1 H2O as it now has both groups on either end. if u add the two eqn u get (2n-1) water
was that ur question?

Yea it was, tysm the diagrams rlly clear it