Be Careful with Organic!
Take a Compound 4-Ketopentan-1-oicacid.
Now carry out the following reactions with it in sequence:
-
Add Glycol , H X + .
-
Add N H X 3 , and heat it .
-
Add H X +
-
Add B r X 2 , K O H
-
Add H X + .
-
Add H N O X 2 , then H X 2 O .
-
Heat it .
What is the Molecular weight of the product formed.
Details and Assumptions :
-
All the step of reaction will happen .
-
Consider only the major product.
This is a part of my set Organo Blasts .
The answer is 72.
This section requires Javascript.
You are seeing this because something didn't load right. We suggest you, (a) try
refreshing the page, (b) enabling javascript if it is disabled on your browser and,
finally, (c)
loading the
non-javascript version of this page
. We're sorry about the hassle.
1 solution
@Aniswar S K , @Harsh Shrivastava @Prakhar Bindal @Sumanth R Hegde. Plz help me here.I proceeded like converting the keto to a protecting group next carboxylic acid to amide.Adding H+ now converts the protecting group back to ketone.Next Hoffman Bromamide degradation to form a compound with a keto +aniline group.Next converting the aniline to. diazonium next the diazonium breaks down and OH attacks.The final product as per me has a molar weight of 88.And another dbt if we are available with hoffman Bromamide and due to presence of a methyl ketone(as in the case here) there is chance of a haloform reaction as well.So which gets preference?
Log in to reply
First protect ketone, then convert carboxylic acid to amide when nh3 is added.
Then h+ converts the acetal to ketone.
Now proceed with both bromoform and Hoffman bromamide reaction.
You should get 3 hydroxy propanoic acid with molecular weight 90
Then when they heat it there are two choices intermolecular or intermolecular ester formation. Both are possible but according to me inter is preferred due to six membered ring formation. But when you heat it both can happen. So answer must be 144 or 72
Log in to reply
Pka of amide is around 18.
Pka of alpha hydrogen next to keto group is 20.
So if at all you want to choose, prefer Hoffman bromamide but precipitation is also a factor to consider in case of haloform!
Well most probably we should do both unless some specific condition is mentioned . Haloform is a veryfast reaction you see coz of the fact that when a carbanion attacks bromine , it being a powerful -I group , the hydrogen becomes more acidic due to strong inductive effect of bromine . An awesome simple problem based on above concept was asked In JEE 2013 Paper 2 . But Indeed it will be a very confusing problem and probably won't be asked except in a FIITJEE AITS or CM Test. As you told about Diazonium being attacked by water do have a look at Tiffeneau–Demjanov rearrangement . Its a very classical case and have a look at its applications of Chair form of cyclohexane (Stereospecific aspects)
Log in to reply
Thanks.... I am getting a lot confused with names..... My God so many people have done so much in Chem... But never do we have the name of an Indian??
Log in to reply
@Spandan Senapati – I Dont think so . i've studied lot of chem in last 2 years . Apart from Raman effect i'ven't found anything india related
Log in to reply
@Prakhar Bindal – I as well....... Isn't this an indication of our teaching methodology or students interest in chemistry....?
Log in to reply
@Spandan Senapati – Of course. People at +2 level (i'm one of them) hated chemistry primarily coz of the teaching structure . At school you get teachers which r just interested in making you learn definitions given in THE CLASSICAL NCERT Textbook (Pun Intended). That makes chem like history . At coaching institutes first you r taught concepts which somewhat make chemistry interesting but when they conduct tests (especially in organic and inorganic) you get poor scores coz of tonnes of exceptions being loaded in the paper . you won't believe i score 12/70 in phase 4 paper 1 chemistry. primarily coz of some or other exceptions in every question , out of syllabus questions in organic (like Favorski rearrangement , Fenton's Oxidation in Fused ring aromatics ) that kind of stuff . Still i didn't loose a single mark in organic chemistry in JEE ADVANCED 2017 both papers .Same thing goes for inorganic . I Remember scoring 15/62 in Open test paper 1 because of shitty things which i heard first time (p3d5 hybridisation!!!! ,stuff called Elb's oxidation etc) .
In my opinion both school and coaching system is screwed in India . that's why no one takes interest in chemistry and most of potentially good students (I Was told in my class 10 by my fiitjee and school teacher that i was pretty good at chemistry but on reaching +1 and +2 i completely lost interest in it) end up developing hatred for chemistry .
Sorry for this long post but i'm really worried about views of students about chemistry which is really alarming
Log in to reply
@Prakhar Bindal – Ya it's true.....Same is the case with me as well..... Inorganic is quite messy...... But how do you rate the level of q asked in jee Chem and fiitjee aits.and one more are the fiitjee aits tough....
Log in to reply
@Spandan Senapati – Tough means thing which requires application of BRAIN . FIITJEE AITS requires you to memorise shitty exceptions which you will hear first time in the paper itself . Rest some problems of physics and maths r too tough or unconventional that its highly unlikely that it will strike ANYONE sitting in the exam itself . That's why highest score mostly is around 240 in a paper of 372 marks and i used to get rank in top 25 with just 210 of 372 . This year's JEE Chemistry was one of the toughest in last 10 years . i've solved all papers from 2007 (since JEE Became objective) but have never came across such kind of chemistry problems ever in any jee paper . But yeah they maintain perfect balance. to compensate for tough chemistry they gave a pretty simple math paper this year while physics was moderate (leave some ambiguous questions in paper 1 and 2)
Log in to reply
@Prakhar Bindal – Ya that's the problem... I was solving a paper yesterday of full test-2,m+p in 2 hrs 25 mins and managed a score of abt 85/156....But maths was tough..... Hey I tried jee advanced paper as per timings got 244(134+110) Although the pressure and expectation are quite high in the exam itself
Log in to reply
@Spandan Senapati – That's a very high score. congratulations!
Log in to reply
@Prakhar Bindal – There's a lot to be done in a year.... And scoring in home is easy.... Actual situation is different. Ya some like that torque question. But you ll surely get a top 50 rank.... BTW what's your aim??
Log in to reply
@Spandan Senapati – Well i'm interested in theoretical computer science and Mathematical computing . I Have to take a decision now
@Spandan Senapati – From FIITJEE Keys i'm getting (164+136) around that . But they are some ambiguities in paper 1 and 2 . let's see what JEE Does
The answer should be 70 according to me
Answer is correct and the product is acrylic acid.
Hey @Aniket Sanghi ... After the second last reaction ... I got my compound as .. "3 amino propanoic acid " whose molecular weight is 89 . After heating , if water eliminates( I am not confirm ) ...the molecular weight should be 71. I got my answer by subtracting 17 , (by mistake).