Use Coupon: CART20 and get 20% off on all online Study Material

Total Price: R

There are no items in this cart.
Continue Shopping
Get instant 20% OFF on Online Material.
coupon code: MOB20 | View Course list

Get extra R 500 off


The classical term ortho effect was quantitatively analyzed and decomposed into its real or supposed components, using the acidity of eleven 2-substituted benzoic acids as a sample. The substituent effects were evaluated by calculations at the B3LYP/6-311+G(d,p) level by means of isodesmic reactions, separately for the acid molecules and for their anions. An intramolecular hydrogen bond, affecting the acidity moderately, was found only in the case of 2-methoxy- and 2-dimethylaminobenzoic acids. For the other acids, the often-employed interpretation invoking a hydrogen bond is wrong: the pertinent form was not revealed by calculations or by infrared spectroscopy. Another widespread explanation relying on the steric inhibition of resonance of the COOH group is also not correct in most cases: only some acid molecules are nonplanar (with substituents tert-Bu, CH2Cl, CF3, NO2, Cl) and the steric inhibition exists also in the anions, thus partly cancelling this effect. The main part of the ortho effect consists of polar effects (inductive and resonance) transmitted through the ring and of purely steric effects. Their tentative separation was based on comparison with the 4-substituted isomers. Polar effects are most important for the acidity and are not very different in the ortho and para positions (rough estimate 0.8:1). Steric effects are strong but mostly of similar magnitude in the acid as in the anion; hence they are of restricted importance for the acidity. They may be better described as van der Waals interactions rather than as short-range field effects. The whole analysis leads to the conclusion that the acidity of ortho-substituted benzoic acids cannot be interpreted by a simple universal theory.

6 years ago


Answers : (1)


Dear student,

The ortho effect if based on the premise that an ortho-substituted acid (take benzoic acid as an example) is more acidic than the meta or para-substituted form. This effect is not dependent on the nature of the substituent (e- donating or e- withdrawing). The reason for this is that the steric hinderance between the substituent and the neighboring carboxylate forces the carboxylate to bend out of the plane of the aromatic ring. This conformational shift alters the delocalization of the charge into the benzene ring, making it easier for the negative charge to be delocalized throughout the pi-system.


Please feel free to ask your queries here. We are all IITians and here to help you in your IIT JEE preparation.

All the best.

Win exciting gifts by answering the questions on Discussion Forum. So help discuss any query on askiitians forum and become an Elite Expert League askiitian.

Now you score 5+15 POINTS by uploading your Pic and Downloading the Askiitians Toolbar  respectively : Click here to download the toolbar..


Askiitians Expert

Sagar Singh

B.Tech, IIT Delhi

5 years ago

Post Your Answer

Other Related Questions on Organic Chemistry

How is pressure inversly proprtion to volume in mole concept??
For a fixed amount of an ideal gas kept at a fixed temperature, pressure and volume are inversely proportional. Or Boyle's law is a gas law , stating that the pressure and volume of a gas...
Umakant biswal 3 months ago
According to Boyle's law or Pressure-Volume Law which state that the volume of a given amount amount gas held at constant temperature varies inversely with the applied pressure when the...
somprasad 3 months ago
chemical bonding molecular structure.covalent bondi,Ionic bond,hybridization
A covalent bond , also called a molecular bond , is a chemical bond that involves the sharing of electron pairs between atoms. These electron pairs are known as shared pairs or bonding...
Umakant biswal one month ago
plsssss tell hybridisation structure of BF3...... and angle , and plsss tell did we get that.
sp2 should be its hybridization. and geometry should be Trignol Planer. and angle should be 120 degree.
Vikas TU one month ago
What is the unit of si(probability amplitude)?Plzz urgent..
@ shivam in quantu mechanics a probability amplitude is a complex number used in describing the behaviour of the system . its unit will be m ^ -3/2 where m is meter . HOPE IT CLEARS NOW ALL ...
Umakant biswal 6 days ago
Sir, i am asking about si which is the probability wave function like for an electron.. I hope u understand
Shivam Raina 6 days ago
Normal atmospheric pressure is 14.7 psi , which means that a column of air one square inch in area rising from the Earth's surface up to space weighs 14.7 pounds. Normal atmospheric...
Umakant biswal 7 days ago
WHAT IS ELECTRO CHEMISTRY........................................?
SAI SARDAR 3 months ago
@ sree the branch of chemistry that deals with the relations between electrical and chemical phenomena... it besically deals with the interconversion of electric current used in chemical...
Umakant biswal 3 months ago
Electrochemistry is the branch of chemistry which deals with electricity produced by chemical reaction and also how electricity can carry out chemical reactions. Hope you understand my...
Adarsh 3 months ago
Show the value of Rydberg constant vary with the mass of the nucleus.
Boher showed the Rydberg’s Constant as a function of the mass of the nucleus. It is given as: R = (alpha)^2*m*c/2h where alpha is the constant with m is the mass of nucleus and c is speed...
Vikas TU 6 days ago
View all Questions »

  • Complete JEE Main/Advanced Course and Test Series
  • OFFERED PRICE: R 15,000
  • View Details
Get extra R 3,750 off

Get extra R 500 off

More Questions On Organic Chemistry

Ask Experts

Have any Question? Ask Experts

Post Question

Answer ‘n’ Earn
Attractive Gift
To Win!!!
Click Here for details