H NMR Topscore

[Jo07]

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I don't understand how on questions 74, test 2 of Topscore m-xylene has four peaks. (in the soluation it says there is a graph or something below but it doesn't show up on my computer).

I thought I was straight on the peaks, but now I'm confused. Also, the singlet,doublet, ect still has me confused.

Can someone help?

 

[DENT2008]

I know this doesn't answer your question, but do you find topscore as helpful as destroyer? I am taking the DAT in a little less than a month and only have Kaplan and Destroyer... do you think I should get Topscore as well? When are you taking your test?

 

[pbure]

I know this doesn't answer your question, but do you find topscore as helpful as destroyer? I am taking the DAT in a little less than a month and only have Kaplan and Destroyer... do you think I should get Topscore as well? When are you taking your test?

topscore is solid but you can live without it

 

[Jo07]

I'll let you know on Friday!

I guess it's just a matter of having an extra test to practice. I pretty much have all the study guides and my least favorite is Achiever. I like destroyer the most though because of the format. I spent a lot of money on crack the pat and achiever to not be using them as much as I should, but hey if I have to retake I'll still have them! 😱

 

[Jo07]

I have another question....

Topscore again.

Gives NH3 and asks for molecular shape. The 3 H and lone pair make it tetrahedral, but it says to ignore the lone pair and make it trigonal pyrimidal. Do we always ignore it? Maybe I'm confusing it with something else.

I guess we only count all the electron clouds if we were doing the sp^3=4? (those are random letters)

 

[shoombol tallah]

I have another question....

Topscore again.

Gives NH3 and asks for molecular shape. The 3 H and lone pair make it tetrahedral, but it says to ignore the lone pair and make it trigonal pyrimidal. Do we always ignore it? Maybe I'm confusing it with something else.

I guess we only count all the electron clouds if we were doing the sp^3=4? (those are random letters)

NH3 is sp3 hybridized. Three bonds with the H's and the lone pair make the nitrogen sp3. For sp3 molecules know that if it has 4 "normal" bonds such as those in CH4 then its tetrahedral with 109.5 degree angles. If its sp3 with one lone pair then its trigonal pyramidal with 107.5 degree angles (NH3). If its sp3 but with two lone pairs like H20 then its called bent with angles of approximately 104.5 i believe. its kinda tricky but easier to see than explain, i suggest looking it up in gen chem text book if you still have one . The pictures will probably make much more sense than my explanation lol.


For your first question the molecule has four peaks. The two methyl groups are equivalent so they show up as 1 peak on the HNMR . They are a singlet because they have no neighboring hydrogens on adjacent carbons. The carbon inbetween the methyl groups is also a singlet because it to has no neighboring hydrogens. The three carbons on the other side of the molecule give two different peaks. The carbon in the middle is a triplet because it has 2 neighboring hydrogens (n+1). And the two carbons on either side of it are equivalent so they give one peak which is a doublet ....again n +1 , so 1+1= doublet. Hope that makes sense!

 

[Jo07]

yes...Thank you! 👍

 

[sacjumpman]

I have another question....

Topscore again.

Gives NH3 and asks for molecular shape. The 3 H and lone pair make it tetrahedral, but it says to ignore the lone pair and make it trigonal pyrimidal. Do we always ignore it? Maybe I'm confusing it with something else.

I guess we only count all the electron clouds if we were doing the sp^3=4? (those are random letters)

Just be careful between if they ask for "electron pair geometry" and "molecular geometry." Make sure you are clear on the difference between the two.