IGCSE/GCSE/O & A Level/IB/University Student Forum

Qualification => Subject Doubts => GCE AS & A2 Level => Sciences => Topic started by: Assi1993 on October 05, 2010, 06:08:42 pm

Title: question relating mass spectra!
Post by: Assi1993 on October 05, 2010, 06:08:42 pm

hi..i dont understand why propanone and propanal have a different mass spectra though they have the same relative molecular mass..i know that they have different structure but how does that effect the spectra????

waiting for the reply !!

Title: Re: question relating mass spectra!
Post by: Deadly_king on October 05, 2010, 06:17:39 pm

Quote from: Assi1993 on October 05, 2010, 06:08:42 pm

hi..i dont understand why propanone and propanal have a different mass spectra though they have the same relative molecular mass..i know that they have different structure but how does that effect the spectra????

waiting for the reply !!

Am sorry I need to run for now. So I won't be able to explain. Try this though:

http://www.chemguide.co.uk/analysis/masspec/fragment.html

http://www.chemguide.co.uk/analysis/masspecmenu.html

http://www.chemguide.co.uk/analysis/masspec/howitworks.html


If you still don't understand, let me know and i'll try as much as I can to clear your doubt :)

Title: Re: question relating mass spectra!
Post by: Assi1993 on October 05, 2010, 06:36:40 pm

Quote from: Deadly_king on October 05, 2010, 06:17:39 pm

Am sorry I need to run for now. So I won't be able to explain. Try this though:

http://www.chemguide.co.uk/analysis/masspec/fragment.html

http://www.chemguide.co.uk/analysis/masspecmenu.html

http://www.chemguide.co.uk/analysis/masspec/howitworks.html


If you still don't understand, let me know and i'll try as much as I can to clear your doubt :)

umm thanks but.....i still didnt get the answer 2 my question :(

Title: Re: question relating mass spectra!
Post by: Deadly_king on October 06, 2010, 06:26:22 am

Ok......i'll try to help.

First you need to draw the structural formula of both compounds :

Propanone :CH₃COCH₃
Propanal : CH₃CH₂COH

Now we can determine the ions that will be produced during mass spectrometry.

For propanone : CH₃⁺, CH₃CO⁺ and H⁺

For propanal : CH₃⁺, CH₃CH₂⁺, CH₃CH₂CO⁺ and H⁺

NOTE : The bonds in C=O does not break since they are very strong bonds.

Since the ions formed are different, their mass spectra will surely be different  ;)

Propanone and propanal may have the same relative molecular mass but the ions produced vary since their structure are different.

Hope it helps :)

Title: Re: question relating mass spectra!
Post by: Assi1993 on October 06, 2010, 01:30:49 pm

Quote from: Deadly_king on October 06, 2010, 06:26:22 am

Ok......i'll try to help.

First you need to draw the structural formula of both compounds :

Propanone :CH₃COCH₃
Propanal : CH₃CH₂COH

Now we can determine the ions that will be produced during mass spectrometry.

For propanone : CH₃⁺, CH₃CO⁺ and H⁺

For propanal : CH₃⁺, CH₃CH₂⁺, CH₃CH₂CO⁺ and H⁺

NOTE : The bonds in C=O does not break since they are very strong bonds.

Since the ions formed are different, their mass spectra will surely be different  ;)

Propanone and propanal may have the same relative molecular mass but the ions produced vary since their structure are different.

Hope it helps :)

ohh !! Thankss!........that helped :) may God bless u :D

Title: Re: question relating mass spectra!
Post by: Deadly_king on October 06, 2010, 02:12:44 pm

Quote from: Assi1993 on October 06, 2010, 01:30:49 pm

ohh !! Thankss!........that helped :) may God bless u :D

You're welcome  ;)

Thank you :)