However, nitrogen groups are not always meta directors. This excess One aspect we’ve covered previously is the concept of “activating” and “deactivating” groups. I wish I’d put that in too. Is it considered as a alkyl group as far a being a o,p, director? 5 - Understanding Periodic Trends, From Gen Chem to Org Chem, Pt. But, what if you have a Ph group as an substituent? Hi James, thank you for the brilliant article? In our next post, we’ll explain the reasons for both ortho-, para- and meta- direction, and try to show why halogens fit in the former category but not the latter. Required fields are marked *. Learning New Reactions: How Do The Electrons Move? [See this previous post on the mechanism of electrophilic aromatic substitution]. Activating substituents: After the first reaction the second (and third if applicable) follow at increased speeds. 6 - Lewis Structures, A Parable, From Gen Chem to Org Chem, Pt. I have my board exams from feb or march. the mechanism of electrophilic aromatic substitution, factors that affect the stability of carbocations, factors which make carbocations more unstable, Understanding Ortho, Meta, and Para Directors. Hence, NO2 is a meta-director, as we all learned The nitration of methylbenzene. Nitro group is electron withdrawing group and thus causes electron deficiency at ortho and para positrons as is clear from the resonating structures of nitro benzene. What if we have a trityl as a substituent? It would be considered an electron donating group, yes – an ortho,para director. Examples: -OH, -NH2, -Me. that is really a wonderful article but something confuses me that what is the trend of halogens when they behave as deactivating ortho para directors which halogen is most de activating and which is least next i want to ask that which is more activating OR or OH. I believe it should be a meta director since the carbon would be quite electrophilic due to the -I effect of the phenyl group. Use these results to state whether -NO2 is an ortho-para directing substituent or a towards electrophilic aromatic substitution. I'm going to assume that when you're talking about m-nitrotoluene, that NO2 is on the 3rd position. Since NO 2 is an electron withdrawing group, a glance at the resonance structures shows that the positive charge becomes concentrated at the ortho-para positions. How To Determine Hybridization: A Shortcut, Sigma bonds come in six varieties: Pi bonds come in one, A Key Skill: How to Calculate Formal Charge, Partial Charges Give Clues About Electron Flow, The Four Intermolecular Forces and How They Affect Boiling Points, How To Use Electronegativity To Determine Electron Density (and why NOT to trust formal charge), How To Use Curved Arrows To Interchange Resonance Forms, Evaluating Resonance Forms (1) - The Rule of Least Charges, How To Find The Best Resonance Structure By Applying Electronegativity, Evaluating Resonance Structures With Negative Charges, Evaluating Resonance Structures With Positive Charge, In Summary: Evaluating Resonance Structures, Drawing Resonance Structures: 3 Common Mistakes To Avoid, How to apply electronegativity and resonance to understand reactivity, The Stronger The Acid, The Weaker The Conjugate Base, Walkthrough of Acid-Base Reactions (3) - Acidity Trends, Acid-Base Reactions: Introducing Ka and pKa, A Handy Rule of Thumb for Acid-Base Reactions, How Protonation and Deprotonation Affect Reactivity, Meet the (Most Important) Functional Groups, Condensed Formulas: Deciphering What the Brackets Mean, Hidden Hydrogens, Hidden Lone Pairs, Hidden Counterions, Primary, Secondary, Tertiary, Quaternary In Organic Chemistry, Branching, and Its Affect On Melting and Boiling Points, Common Mistakes: Drawing Tetrahedral Carbons, Common Mistakes in Organic Chemistry: Pentavalent Carbon, Table of Functional Group Priorities for Nomenclature, Organic Chemistry IUPAC Nomenclature Demystified With A Simple Puzzle Piece Approach, Staggered vs Eclipsed Conformations of Ethane, Newman Projection of Butane (and Gauche Conformation), Geometric Isomers In Small Rings: Cis And Trans Cycloalkanes, Calculation of Ring Strain In Cycloalkanes, Cycloalkanes - Ring Strain In Cyclopropane And Cyclobutane, Cyclohexane Chair Conformation: An Aerial Tour, How To Draw The Cyclohexane Chair Conformation, The Cyclohexane Chair Flip - Energy Diagram, Substituted Cyclohexanes - Axial vs Equatorial, Ranking The Bulkiness Of Substituents On Cyclohexanes: "A-Values". 10 - Hess' Law, From Gen Chem to Organic Chem, Pt. Your email address will not be published. Interesting,though the principles that guide ortho,meta and para directors does not come out clearly, Why is a meta-product major and ortho-para-products minor? CH3 groups are ortho-para directing, so you could either place the 3rd group (CH3+) on position 2, 4, or 6. 13 - Equilibria, From Gen Chem to Organic Chem, Part 14: Wrapup, How Concepts Build Up In Org 1 ("The Pyramid"), Review of Atomic Orbitals for Organic Chemistry. However, the first place to start is that it has to do with the stability of the carbocation intermediate in electrophilic aromatic substitution reactions. What are alkynes considered? Two Important Reaction Patterns: Ortho- , Para-Directors and Meta-Directors It’s one thing to learn about electrophilic aromatic substitution reactions of benzene itself. What is up with the halogens, and how is it that they can be deactivating (i.e. What is the resonating structure of -CHO?? Thus these positions are deactivated towards electrophilic aromatic substitution. activating groups show electron density at ortho - para so that they called ortho - para directing groups the NO2 is electron withdrawing group as it no contains lone pair electron withdrawing group is known as.
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