This is precisely the result that the drawing of resonance structures would predict. They have overlap on the carbon-hydrogen bonds (or carbon-carbon bonds in compounds like tert-butylbenzene) with the ring p orbital. Electron withdrawing group (EWG): An atom or group that draws electron density from neighboring atoms towards itself, usually by resonance or inductive effects. 1. EDG stands for electron donating groups. Thus, we can use these simple species, whose π electron distribution can be calculated using simple Hückel theory, as models to rationalize the regiochemical outcome of electrophilic aromatic substitution. EDGs are therefore often known as activating groups, though steric effects can interfere with the reaction. The below infographic lists out more details on the difference between EDG and EWG. Electron donating groups are typically divided into three levels of activating ability (The "extreme" category can be seen as "strong".) This can also explain why phosphorus in phosphanes can't donate electron density to carbon through induction (i.e. What is EDG Protecting your private information is our priority. Our goal? All rights reserved. More specifically, any formal negative or positive charges in minor resonance contributors (ones in accord with the natural polarization but not necessarily obeying the octet rule) reflect locations having a larger or smaller coefficient, respectively, in the high energy occupied π molecular orbital(s). (That's 1013 times more acidic than hydrofluoric acid). The carbon on that is sp3 hybridized and less electronegative than those that are sp2 hybridized. The key difference between EDG and EWG is that the EDG (stands for Electron Donating Groups) can increase the electron density of a conjugated pi system whereas the EWG (stands for Electron Withdrawing Groups) decreases the electron density of a conjugated pi system. However, the lone pair of its monomer form is unfavourable to donate through resonance. While all deactivating groups are inductively withdrawing (–I), most of them are also withdrawing through resonance (–M) as well. These are organic compounds containing an alkyl chain with an amine group bound to the C1 atom and an alcohol group bound to the C2 atom. ERG’s solution is chemistry-based, using heat and chemicals in a reactor to destroy pathogens and transform the waste into a beneficial soil conditioner and plant nutrient source. Earth Renewal Group (ERG) offers an advanced, chemistry-based solution for converting organic waste streams into Exceptional Quality* (EQ) biosolids for agricultural use. Both EDG and EWG are electrophilic aromatic directing groups. The negative oxygen was 'forced' to give electron density to the carbons (because it has a negative charge, it has an extra +I effect). Weakly deactivating groups direct electrophiles to attack the benzene molecule at the ortho- and para- positions, while strongly and moderately deactivating groups direct attacks to the meta- position. Notice that iodobenzene is still less reactive than fluorobenzene because polarizability plays a role as well. However, benzene usually undergoes this type of electrophilic substitution reaction. In general, the resonance effect of elements in the third period and beyond is relatively weak. This makes the pi electron system more nucleophilic. The Hammond postulate then dictates that the relative transition state energies will reflect the differences in the ground state energies of the Wheland intermediates. it produces small positive charges on the ortho and para positions but not on the meta position and it destabilises the Wheland intermediate.) (Positively charged nitrogen atoms on alkylammonium cations and on nitro groups have a much stronger -I effect). Yes, electron withdrawing groups (EWG). When both group are the same director, the third substituent depends on the stronger one. Hunt, Ian R. “Ch12: Substituent Effects.” Ch 13 – NMR Basics. To change the way communities worldwide address the growing challenge of organic waste disposal and nutrient recovery through the application of renewable, sustainable, economically sound technology. A carbon atom with a larger coefficient will be preferentially attacked, due to more favorable orbital overlap with the electrophile. Hence the result is that they are EDGs and ortho/para directors. As a result, the nitroso group is a deactivator. Aside from these effects, there is often also a steric effect, due to increased steric hindrance at the ortho position but not the para position, leading to a larger amount of the para product. Both these substituents show significant effects on the electrophilic substitution reactions of conjugated pi systems such as benzene ring; EDG can increase the reaction rate of electrophilic substitution reactions of aromatic rings whereas EWG can decrease the reaction rate of electrophilic substitution reactions of aromatic rings. Even when cold and with neutral (and relatively weak) electrophiles, the reaction still occurs rapidly. Multiple Multiple Substituent Substituent Effects", "XXX.—A rule for determining whether a given benzene mono-derivative shall give a, https://en.wikipedia.org/w/index.php?title=Electrophilic_aromatic_directing_groups&oldid=973313650, Creative Commons Attribution-ShareAlike License. On the other hand, iodine directs to ortho and para positions comparably (54% para and 45% ortho, 1.3% meta).[10]. Available here, 1.”Nitrobenzene resonance”By Ed (Edgar181) – Own work, (Public Domain) via Commons Wikimedia.