Ortho meta para position in benzene

\( \newcommand\) No headers A monosubstituted benzene, when treated with an electrophile, could undergo three electrophilic aromatic substitution reactions. Each reaction yields a disubstituted benzene as the organic product, which can be identified using the descriptors ortho, meta, and para (see ortho carbon). A = any substituent E + = electrophile If the relative yield of the ortho product and that of the para product are higher than that of the meta product, the substituent on the benzene ring in the monosubstituted benzene is called an ortho, para directing group. If the opposite is observed, the substituent is called a meta directing group. eg. 1: Thus, the methyl group is an ortho, para directing group. eg. 2: Thus, the nitro group is a meta directing group. Ortho, para directing groups are electron-donating groups; meta directing groups are electron-withdrawing groups. The halide ions, which are electron-withdrawing but ortho, para directing, are the exception. Common ortho, para directing groups: Common meta directing groups: see also

\( \newcommand\) • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • Objectives After completing this section, you should be able to • draw the structure of each of the common aromatic compounds in Figure 16 (Common benzene derived compounds with various substituents), given their IUPAC-accepted trivial names. • write the IUPAC-accepted trivial name for each of the compounds in Figure 16, given the appropriate Kekulé, condensed or shorthand structure. • identify the ortho, meta and para positions in a monosubstituted benzene ring. • use the ortho/meta/para system to name simple disubstituted aromatic compounds. • draw the structure of a simple disubstituted aromatic compound, given its name according to the ortho/meta/para system. • provide the IUPAC name of a given aromatic compound containing any number of the following substituents: alkyl, alkenyl or alkynyl groups; halogens; nitro groups; carboxyl groups; amino groups; hydroxyl groups. • draw the structure of an aromatic compound containing any number of the substituents listed in Objective 6, above, given the IUPAC name. • provide the IUPAC name of a given aromatic compound in which the phenyl group is regarded as a substituent. • draw the Kekulé, condensed or shorthand structure of an aromatic compound in which the phenyl group is regarded as a substituent, given its IUPAC name. Study Notes You should already know the names and structures of several of the hydrocarbons shown in Figure 15.1. A compound con...

Electron donators / Activators (strongest to weakest): -O -, -NR 2, -NH 2, -OH, -OR, -R Electron Withdrawers / Deactivators (strongest to weakest): -NO 2, -NR 3 +, -NH 3 +, -SO 3H, -CN, -CO 2H, -CO 2R, -COH Generally speaking, electron donators / activators have a lone pair of electrons or an electron density that “pushes” into the benzene. Electron withdrawers / deactivators have a positive charge on the substituent or a very electronegative atom attached to it, which “pulls” electrons out of the benzene. All activators AND halogens are ortho-para directors; Deactivators (not halogens) are meta-directing. Therefore, depending on the character of the initial substituent (R), a subsequent substituent would be placed at the ortho or para position if R is an activator/halogen or at the meta position if it is a deactivator (but not a halogen). Other facts to know: • The more electron donating groups a benzene ring has initially, the faster an EAS reaction will occur (due to increased electron density to make benzene a better nucleophile). • If there are already two or more substituents on the ring, the strongest donating group gets priority when choosing the location of the added substituent. • When given an ortho / para choice, substituents will go to the location with the least steric strain.

Introduction There are two main effects of substituents. The substituent will affect the rate of reaction (aka reactivity) of the ring, and it will also affect the position of attack (called “directing effects”) on the ring by the incoming electrophile. Thus we need to answer the following questions: • Does the substituent activate or deactivate the aromatic ring? • Where will the incoming group go? Reactivity: Activation and deactivation Because benzene acts as a nucleophile in electrophilic aromatic substitution, substituents that make the benzene more electron-rich can accelerate the reaction. Substituents that make the benzene moor electron-poor can retard the reaction. In the mid-twentieth century, physical organic chemists including Christopher Ingold conducted a number of kinetic studies on electrophilic aromatic substitution reactions. In table 1, you can see that some substituents confer a rate of reaction that is much higher than that of benzene (R = H). Phenol, C 6H 5OH, undergoes nitration a thousand times faster than benzene does. Nitrobenzene, C 6H 5NO 2, undergoes the reaction millions of times more slowly. Table : Rate of nitration in benzene derivatives R in C 6H 5R Relative rate OH 1,000 CH 3 25 H 1 CH 2Cl 0.71 I 0.18 F 0.15 Cl 0.033 Br 0.030 CO 2Et 0.0037 NO 2 6 x 10 -8 NMe 3 + 1.2 x 10 -8 These observations are consistent with the role of the aromatic as a nucleophile in this reaction. Substituents that draw electron density away from the aromatic ring ...

Why ortha para directors activate the benzene ring? Ortho-para directing groups are those which can donate the electrons (lone pair or bonding pair by hyperconjugation) to benzene ring and create a negative charge on ortho and para positions by process of resonance so the attack of next incoming electrophile becomes easier as compare to unsubstituted benzene.

In this post, we will talk about the ortho-, meta and para directors in electrophilic aromatic substitution (EAS). As a reminder, the ortho-, meta and para are the relative positions of the two groups in a disubstituted aromatic ring: Depending on the group (X) that is initially present on the benzene ring, the second substituent goes either to ortho/para or the meta position: Here is the short answer to ‘how do I know if the electrophile will go to ortho, para or meta position?’ Any Activating group directs the electrophile to the orthoand parapositions. Any deactivating group directs the electrophile to the metaposition. An activated ring means it undergoes an electrophilic aromatic substitution faster than benzene and deactivated rings react slower than benzene. The activation and deactivation of the aromatic ring are caused by inductive or resonance effects (or both). The inductive effect is a result of different electronegativities of the carbon in the ring and the atom connected to it. There can be electron-donating (activating) and electron withdrawing (deactivating) groups. For example, a methyl group activates the ring since the carbon is connected to three hydrogens and being more electronegative it pulls the electron density and donates to the ring. And, in general, any alkyl group is an activator. Halogens, on the other hand are more electronegative than carbon and when connected to the ring, they pull the electron density by the inductive effect and thus reduc...

Columns | Column: IR Spectral Interpretation Workshop With the theoretical background of benzene analysis laid out in part 1 of this series, we now know what fundamental, overtone, and combination bands look like. Here, I show that the benzene fingers are a series of overtone and combination bands that can be used to distinguish substituted benzene rings from each other when other methods do not work. I review the benzene finger patterns for mono-, ortho-, meta-, and para- substituted benzene rings, and describe an easy mnemonic in which you use your fingers to help you remember the patterns. With the theoretical background of benzene analysis laid out in part I of this series, we now know what fundamental, overtone, and combination bands look like. Here, we show that the benzene fingers are a series of overtone and combination bands that can be used to distinguish substituted benzene rings from each other when other methods do not work. We also review the benzene finger patterns for mono-, ortho-, meta-, and para-substituted benzene rings, and describe an easy mnemonic in which you use your fingers to help you remember the patterns. In an earlier installment (1), I introduced the chemical structures and nomenclature for mono- and disubstituted benzene rings, and showed how the presence or absence of the ring bend at 690 ± 10 cm -1 and the position of the out-of-plane aryl C-H wag together can be used to distinguish mono-, ortho-, meta-, and para-isomers from each other. T...