way to remember o/p & meta directing groups??

[Topper Harley]

if anyone has a stumbled on a more efficient way to remember the groups that are, ortho/para activating, ortho/para decativating and meta deactivating groups, (other than just memorizing) it would be much appreciated.

Thanks
~Topper

---

Members don't see this ad.

 

[firebird69guy]

mnemonic:

if you donate e to the ring, you will get more possibilities (ortho, para)

if you take away e from the, you will get fewer possibilities (meta)

-------------

now, the way to know if they donate or take away is to just look at the electronegativies of the elements attached to the atom bound to the benzene ring. If they are more electronegative, then the overall effect is taking away e = meta directing (including halides). If they are less electronegative, the overall effect is adding e to the ring, ortho para directing. Also, if the atom is positively charged (like a nitrogen+), it will withdraw electrons.


Hope this helps.

 

[OrGoMan]

dident they take Arene chemistry off the mcat for april? that means to ortho, meta directors crap. NO BENZENE!!!

 

[Fusion]

dident they take Arene chemistry off the mcat for april? that means to ortho, meta directors crap. NO BENZENE!!!

True. It is worth knowing, but definitely do not emphasize ortho/meta/para directors during your MCAT preparation.

 

[Tinker Creek]

dident they take Arene chemistry off the mcat for april? that means to ortho, meta directors crap. NO BENZENE!!!

Really?? what else? Where could I find what's ommitted or not?

 

[Turkeyman]

lol EK has a big mnemonic for this one...its kinda interesting, but helps me remember

So you have uncle Ben(Benzene), and he's a lazy leech.
If you lend him money to go party(electron donating), he'll love you, and want you sit across or next to him at the dinner table (ortho/para).
If you don't lend him any money, he'll hate you and want at least 1 person between you and him (meta).

One exception is that Uncle Ben respected Uncle Hal (halides) even if he didnt give Ben any electrons, because of his character. So, in effect, he would always let Uncle Hal sit across or next to him at the dinner table.

Now, all you have to remember is what's withdrawing or not, and the rest will come...that's not too hard.

 

[Fusion]

Really?? what else? Where could I find what's ommitted or not?

The MCAT section of the AAMC website has a link that lists/details all of the topics that are fair game for the big test.

 

[Turkeyman]

so no more benzene? whaat?

 

[stoleyerscrubz]

http://www.aamc.org/students/mcat/update.htm#content

MCAT Update Announcement
Beginning with the 2003 MCAT administrations the broad structure of the MCAT was maintained, but with the following changes:

Content
Three questions on DNA and genetics were added to the Biological Sciences section. In the biology portion of Biological Sciences, one new topic, "Molecular Biology: Eukaryotes," has been added. Note that this topic falls within the content typically covered in undergraduate introductory science courses. The three additional DNA and genetics questions are included under the topics, "Molecular Biology: Eukaryotes" and "Molecular Biology: DNA and Protein Synthesis."

Topics (PDF, 5 pages - 99KB)

In the organic chemistry portion of Biological Sciences, the topics, "Oxygen Containing Compounds" and "Hydrocarbons" are reduced by a total of three questions. Under the topics, "Hydrocarbons" and "Oxygen Containing Compounds," sub topics Alkenes, Benzene, Phenols, and Ethers were deleted. Some questions may, however, refer to these sub topics. In such cases, relevant information on these sub topics will be provided.

 

[Turkeyman]

wow....no more alkenes...benzene....ethers.... ;0
Less hydrocarbons.....oxygen containing compounds = fatty acids? Bleh...might be better to study it all anyways

 

[liverotcod]

wow....no more alkenes...benzene....ethers.... ;0
Less hydrocarbons.....oxygen containing compounds = fatty acids? Bleh...might be better to study it all anyways

Alcohols and carbonyls (aldehydes, ketones, carboxylates).

 

[QofQuimica]

lol EK has a big mnemonic for this one...its kinda interesting, but helps me remember

So you have uncle Ben(Benzene), and he's a lazy leech.
If you lend him money to go party(electron donating), he'll love you, and want you sit across or next to him at the dinner table (ortho/para).
If you don't lend him any money, he'll hate you and want at least 1 person between you and him (meta).

One exception is that Uncle Ben respected Uncle Hal (halides) even if he didnt give Ben any electrons, because of his character. So, in effect, he would always let Uncle Hal sit across or next to him at the dinner table.

Now, all you have to remember is what's withdrawing or not, and the rest will come...that's not too hard.

lol, I love this! I will have to tell my organic class this one in a couple of weeks when we start studying electrophilic aromatic substitution.

 

[Turkeyman]

lol, I love this! I will have to tell my organic class this one in a couple of weeks when we start studying electrophilic aromatic substitution.

Hahah cool =D

Hey guys...so wtf.....no more C=O stuff and alkenes? wtf isnt that like...all of orgo?

So is it just like chirality, alkanes, and lab techniques now?

seriously, wtf? hahaha

And can someone give me the scope of what "Molecular Biology: Eukaryotes" questions might entail?

Thanks!

 

[borisd]

Hi, I Just studied this today in o chem class. My professor said if you can remember just the ortho/para groups (which is about ten or so) everything else would have to be meta. Ortho is next to the substiuent, meta is the middle and para is next. I totally understand now. Hope it helps!

 

[Aladdin Sane]

my professor beat ortho/para and meta directors into our heads so much that I just have them all memorized, by heart, which is so sad 🙂

anyway maybe this will help: if you know your deactivators (nitrates, sulfate, bulky acylates), almost all deactivators are meta directors. except halides which are deactivators but have to be the jerks of the group and are ortho/para directors.

and all activators are pretty much ortho/para directors

 

[MeowMix]

look, this is a key point that you all are going to be learning very soon in med school:

DO NOT WASTE TIME LEARNING STUFF THAT ISN'T GOING TO BE ON THE TEST!!!! and that definitely includes o,m,p and a bunch of other stuff related to alkynes etc. (you still must know C=O and reactions, very important)

I know you all are into the spiritual perfection of mastery of knowledge, but now is a good time to start letting go of that ideal. Do it now or do it in a year or two at med school.