Chem expert please help...

[Hadi Bakhsh]

Why electrophile does not attack on electron withdrawing group in substituted benzene ?

Benzene molecule is easily attacked by electrophile because nucleophilc character ( more electron density around benzene ring) but when any substituent is attached then it withdraws electron density toward it self and make benzene less reactive then why electrophile does not attack on that group which posses more electron density ? and SHAPE OF BENZENE MOLECULE IS PLANAR OR PLANE HEXAGONAL OR ONLY HEXAGONAL ?
PLEASE ANSWER AS SOON AS POSSIBLE .

[Chintoo2010]

Electrophile means a species which likes Electrons.

Electrons in benzene are delocalized i.e they are like a cloud of electrons hovering above and below the benzene ring on the six carbon atoms due to resonance.

This movement of electrons in benzene make it a Nucleophile.

However, when an Electron Withdrawing Group (EWG) is attached to a ring like NO2, CN, SO3, etc etc. Electrons of the ring are delocalized over a larger regions i.e they are pulled towards that EWG and they circulate on the EWG as well. Net Effect is that Nu character of benzene by virtue of resonating electrons on six C-Atoms is reduced as electrons are less available in the ring in presence of a EWG as compared to a benzene without an EWG. So the availability of the delocalized electrons is reduced to the extent of strength of the EWG and hence this less availability of electrons reduce Nu character and reduce the activity of Benzene towards Electrophilic Substitution Reactions.

( Example A boy (benzene) is in love with a girl (Electrophile). The Girl lives just next door and the boy always avails chance of meeting her (Electrophilic Substitution). But the boy is afraid of his own father and when his father (Electron Withdrawing) is around, he avoids meeting or seeing that beloved girl.

Now your questions that why a E-phile does not react with a EWG when it has pulled electron density of benzene ring towards itself by resonance.
Electrons withdrawn do not always remain in the EWG molecule they keep coming and going from ring to and fro so they are not permanent electrons of the EWG.

Also how an EWG can attract electrophile towards itself when it has borrowed electrons of benzene ring.

Electron density acquired by resonance does not make a electrophile a nuclephile.

How would you make a NO2 to attract a electrophile???It is impossible.
A donkey can not run faster as a horse if even the saddle of horse is placed on its back.

Think clearly and logically in Organic Chemistry.

I hope i have understood your Question.

Structure of benzene is planar.

[Hadi Bakhsh]

may ALLAH SUBHAN WA TA'LA bestow you with a lot of respect and increase your approach to knowledge...
i have some other confusion, i'll be posting please answer these with explanation. i will be thankful to you
1. Benzene has planar shape, but i cant differentiate between Plane hexagon and Planar ?
2. Benzene does not give addition reaction under normal condition because of Resonance which gives more stability to it or delocalized pi electron

and some other points i will post later because i haive no that paper where i have written these, i'll be waiting

[Chintoo2010]

Dear Brother
You are making a hotchpotch of things and making a Pudding of benzene and thinking which you should not think.
Benzene is Hexagonal i.e has six corners. Keep it simple.
It is planar i.e all C-C are 120 angles.
What is the magic in term Hexagonal Planar?? Why are you chasing it so overwhelmingly??? This is result-less tension which you are rendering to yourself.


Addition Reactions.

If Benzene Adds something to it..i.e its C-C double bonds will become single bonds so a hexane will end with each carbon with two substituents and two C-C single bonds hence the molecule will become highly strained and will be far less stable due to steric hindrance.

Now in details
In Benzene

Each C atom has
Two C-C Single bonds...
One C-C double bond ....
One C-H single bond.
Due to 120 angle all bonds are planar and planar structure renders sterically stable Benzene Ring and very less steric hindrance is present.


Whereas if it undergoes a addition reaction then

double bonds become single bonds 109.5 degree and substituents are spread in space and cause strain to the ring and deshape it due to steric strain as it is no more a planar structure.

In Benzene only 6 substituents i.e one H-atom to each C-atom
In Cyclohexane 12 substituents so strain is increased.
(For example in a room of two beds, to students can live easily each occupying his own bed. When you stuff the room with 6 students then things change entirely. Two guys sharing a bed and 3rd one lying under the bed or suspended in space................!)


Benzene Ring is stabilized by resonance structure i.e it has mant canonical forms and more the number of cannonical forms more stable the molecule will be. Resonance structure make it a stable molecule in comparison to a Cyclohexane by a considerable amount of Heat(you can find in book), so when the ring undergoes an additioj reaction it surely loses double bonds and hence loses the stability due to resonance, so it is highly reluctant to give add rxns, Boss.


(Aik pyari si choti si nanhi munni larki k sar par uski mama ny simple c kanghi kr k 2 choatiyaa bna k hair clip lga dia hai jis mai wo bht pyari lg rahi hai (think it as a benzene ring) , aap khud btayen iski jga aik chiryo ka ghonsal (cyclehexane) us k sarr per rakh dia jaye to konsa behtr hai


Read a good book your concepts are not clear as yet these are very basic things. Hit thanks if you like and you are always welcome.

[Hadi Bakhsh]

brother you are right my concepts are not clear as much as should be being a student of MSc so i always try to clear it by asking teachers, friends and the person who have knowledge so please do not mind if ask foolish question because i will ask such thing that confuses me not that i know either it is easy or difficult. PLEASE MENTION SUCH A BOOK THAT COVERS ALSO BASIC CONCEPTS OF ORGANIC CHEM, i have Organic Chem 3rd edition by Bruice, Organic chem by BS Bahal.
actually i have given assigment to solve 152 MCQ with explation that i am asking
and i myself trying to go through it and which MCQ puzzle me i w'll ask on forum and specially you and thanks to you so much.
1.Benzene on treatment with HCN and HCl in presence of anhydrous AlCl3 followed by hydrolysis form A.Cholrobenzene B.Benzoic acid C.Ethyl Benzene D.Cynobenzene
2. Maijor source of bezene A.Coal tar B. Perolum C. Kerosen D. Natural gas ( in books both are maijor source A & B)
3. The ratio of sigma and pi bonds in benzene A.2 B.4 C. 6 D. 8
4. Thiophene is seprated by benzene by A. Sulphonation of benzene B.Sulphonation of thiophene C.Nitration of thiophene D.Oxidation of thiophene

whenn Oxygen is directly attached to two carbonyl groups is called acid anhydride but when NH is bonded instead of oxygen then what is called that ?