Examples of ortho-, para– directors are hydroxyl groups, ethers, amines, alkyl groups, thiols, and halogens. Examples: -OH, -NH2, -Me. The nitro group strongly deactivates the benzene ring towards electrophilic substitution. Examples: -CF3, -NO2, -CN. Yes, Nitro-group is meta-directing. 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Free Radical Initiation: Why Is "Light" Or "Heat" Required? The group is nitro- and not nitrobenzene in this case. It deactivates benzene ring towards electrophilic substitution reaction. This excess This is the kinda answer I was looking for . 1 - The Atom, From Gen Chem to Organic Chem, Pt. Thoughts? 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Since NO2 is an electron withdrawing group, a glance at the resonance structures shows that charge becomes concentrated at the ortho-para positions, as shown by the resonance structures above. If you look through the list of ortho- , para- directors, you might recognize that many of them are also activating groups. More specifically, how does each substituent affect the stability of that intermediate? 9 - Acids and Bases, From Gen Chem to Organic Chem, Pt. ). Great article! slow down the reaction rate) and yet lead to ortho-, para- products? In the second pattern, the meta– product dominates, and the ortho- and para– products are minor. How do ortho-, para- and meta– directors differ, and how could this difference affect the product distribution? Your email address will not be published. Resonating structure of nitrobenzene shows +ve charge develops in ortho and para positions. 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Cyclohexane Chair Conformation Stability: Which One Is Lower Energy? Monochlorination Products Of Propane, Pentane, And Other Alkanes, Selectivity in Free Radical Reactions: Bromination vs. Chlorination, Introduction to Assigning (R) and (S): The Cahn-Ingold-Prelog Rules, Assigning Cahn-Ingold-Prelog (CIP) Priorities (2) - The Method of Dots, Types of Isomers: Constitutional Isomers, Stereoisomers, Enantiomers, and Diastereomers, Enantiomers vs Diastereomers vs The Same? Two important reaction patterns are observed. But once you move beyond benzene, that’s when things start getting really interesting.. Today we’ll describe the two main patterns by which substituents “direct” electrophilic aromatic substitution. Substituents which lead to this result are called, “ortho-, para- directors”. Planning Organic Synthesis With "Reaction Maps", The 8 Types of Arrows In Organic Chemistry, Explained, The Most Annoying Exceptions in Org 1 (Part 1), The Most Annoying Exceptions in Org 1 (Part 2), Screw Organic Chemistry, I'm Just Going To Write About Cats, On Cats, Part 1: Conformations and Configurations, The Marriage May Be Bad, But the Divorce Still Costs Money. Activating substituents: After the first reaction the second (and third if applicable) follow at increased speeds. What is the resonating structure of -CHO?? 8 - Ionic and Covalent Bonding, From Gen Chem to Org Chem, Pt. What are alkynes considered? 3 - Effective Nuclear Charge, From Gen Chem to Organic Chem, Pt. If you substitute a nitro group, -NO 2, into the benzene ring in methylbenzene, you could possibly get any of the following products:. Save my name, email, and website in this browser for the next time I comment. Electrophilic substitution in methylbenzene. 2 - Electrons and Orbitals, From Gen Chem to Organic Chem, Pt. Excellent question. So, in this case, since CH3 is a greater activator / EDG than a NO2 group, CH3 takes precedence over NO2. 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? Examples: -CF3, -NO2, -CN, -F, -Cl, -Br, -I. Ortho, para-directing: Substituents which directs electron density onto the ortho and para positions. As a result, the electron density at meta position … Thus these positions are deactivated towards electrophilic aromatic substitution. in organic chemistry. substitution increases reactivity. First: no activating groups are meta directors. That is a great point. How Gen Chem Relates to Organic Chem, Pt. 10 - Hess' Law, From Gen Chem to Organic Chem, Pt. Hi there, Is -CH₂OH an Ortho Para director or Meta Director? Is it considered as a alkyl group as far a being a o,p, director? But how does this ortho para affect the difference in boiling points and melting points when it comes to isomerism. group is an ortho-para director, as we learned in organic chemistry. towards electrophilic aromatic substitution. Selectivity between the sites is often decided by steric effects. If you’re a real nerd, you could even make a 2 × 2 matrix, like this: Yes indeed. learned in organic chemistry. “In the second pattern, the meta– product dominates, and the ortho- and meta– products are minor.” Just FYI, I think you meant to say “ortho- and para- products are minor” :). Your email address will not be published. I'm going to assume that when you're talking about m-nitrotoluene, that NO2 is on the 3rd position. It would be considered an electron donating group, yes – an ortho,para director. Deactivating substituents: Reaction stops after the first substitution. Diels-Alder Reaction: Kinetic and Thermodynamic Control, Electrocyclic Ring Opening And Closure (2) - Six (or Eight) Pi Electrons, Regiochemistry In The Diels-Alder Reaction, "Is This Molecule Aromatic?" software to draw appropriate resonance structures. This site uses Akismet to reduce spam. 11 - The Second Law, From Gen Chem to Org Chem Pt. Acid Catalysis Of Carbonyl Addition Reactions: Too Much Of A Good Thing? Hence substitution occurs preferentially on those sites. You have three phenyl groups which could interfere with your desired EAS. In the second pattern, a different family of substituents direct the reaction to give primarily the “meta” (1,3) product. Similarly, determine whether -CH3 is ortho-para directing or meta-directing substituent 5 - Understanding Periodic Trends, From Gen Chem to Org Chem, Pt. I.e. Explain whether or not this One aspect we’ve covered previously is the concept of “activating” and “deactivating” groups. 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. Ortho/para directors or meta directors?? What's The Alpha Carbon In Carbonyl Compounds? Hence, NO 2 is a meta-director, as we all learned in organic chemistry.. for electrophilic aromatic substitution. Examples: -OH, -NH2, -Me, -F, -Cl, -Br, -I. Meta-directing: Substituents which draw electron density from the ortho and para positions, hence increasing reaction on the meta position. ortho- and para- products dominate, while meta– products comprise less than 3%. Why would you choose to have trityl as a substituent?
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