Q19 Bauklkham Hills. Module 7 addition polymerization (2 Viewers)

[synthesisFR]

If you did Ruse, did you find it much more difficult than other trial papres? Saw their 2021 paper, and that shit's insane.

All gir- I mean all chem trial papers are the same

 

[carrotsss]

All gir- I mean all chem trial papers are the same

yeah pretty much

i haven’t done ruse papers yet but all good papers I have done feel pretty much identical like there aren’t really many ways to make papers harder other than more long response qs where you lose 1 or 2 marks

 

[Interdice]

 

[Interdice]

Shouldn't there be 3 C environments?

 

[Interdice]

 

[Interdice]

The CH3 is the same on the first diagram

 

[nsw..wollongong]

Shouldn't there be 3 C environments?

C1 is attached to a carbonyl group
C2 = double bonded O (carbonyl) attached to CH3 and CH2
C3 = attached to carbonyl group and CH3
C4 = CH3 attached to CH2

put rlly simply all these groups are different bc they're attached to diff things, so 4 diff environments

 

[Luukas.2]

Extending on @nsw..wollongong's post:

There are two isomeric pentanone's:

• 2-pentanone, CH₃-CO-CH₂-CH₂-CH₃, in which there are 5 x C environments and 4 x H environments, because the molecule is not symmetrical about the carbonyl group (-CO-), and
• 3-pentanone, CH₃-CH₂-CO-CH₂-CH₃, in which there are 3 x C environments and 2 x H environments, because the molecule is symmetrical about the carbonyl group (-CO-).

Similarly, 5-nonanone will have only 5 x C environments and 4 x H environments, whereas 2-nonanone, 3-nonanone, and 4-nonanone will all have 9 x C environments and 8 x H environments. It does not matter how far away any differences might be, each environment that is not absolutely identical to another will count as a separate environment.

 

[Interdice]

 

[Interdice]

 

[Interdice]

How can we tell if it's an aldehyde or ketone?

 

[Luukas.2]

It's a ketone. Aldehydes have medium to strong bands (usually two of them) below the regular C-H band for the C-H of the terminal -CHO - somewhere like 2700 - 2800 cm^-1.

The IR spectrum for propanal can be seen at https: / / webbook.nist.gov/cgi/cbook.cgi?Spec=C123386&Index=0&Type=IR&Large=on&SVG=on (take out the spaces around the slashes) - you'll see that the extra aldehydic C-H bands are prominent.

 

[Interdice]

It's a ketone. Aldehydes have medium to strong bands (usually two of them) below the regular C-H band for the C-H of the terminal -CHO - somewhere like 2700 - 2800 cm^-1.

The IR spectrum for propanal can be seen at https: / / webbook.nist.gov/cgi/cbook.cgi?Spec=C123386&Index=0&Type=IR&Large=on&SVG=on (take out the spaces around the slashes) - you'll see that the extra aldehydic C-H bands are prominent.

Thanks. I read that section like 5 times on the pearson textbook, and I swear that isn't there

 

[Luukas.2]

Most texts / teachers / tutors don't point out that the C-H bands can be informative. The bands at lower wavenumber for an aldehyde are the most obvious, but signals above the usual range can also help, reflecting H-C=C, H-C(aromatic, like a benzene ring), and H-C(alkyne). All are sharp and completely unlike an N-H or O-H band.

 

[Interdice]

Where to get Proton NMR questions?

There are barley any resources on them. Past trial papers don't have proton NMR usually. Where can I get questions.

I also don't want to start HSC exam papers yet.

 

[Interdice]

Are pressure questoins in the scope of this course? Never seen them before