Nucleophilic substitution reaction

• A nucleophile is an electron-rich species that can donate a pair of electrons • ‘Nucleophile’ means ‘nucleus/positive charge loving’ as nucleophiles are attracted to positively charged species • Nucleophilic refers to reactions that involve a nucleophile • There are various different species which can behave as nucleophiles, and some make better nucleophiles than others A hydroxide ion is a better nucleophile as it has a full formal negative charge whereas the oxygen atom in water only carries a partial negative charge • A nucleophilic substitution reaction is one in which a nucleophile attacks a carbon atom which carries a partial positive charge • An atom that has a partial negative charge is replaced by the nucleophile • Halogenoalkanes will undergo nucleophilic substitution reactions due to the polar C-X bond (where X is a halogen) Due to large differences in electronegativity between the carbon and halogen atom, the C-X bond is polar Make sure your arrows are clearly curly - if they are not curly enough then you will not be awarded the mark.Your first arrow must start at the lone pair of the nucleophile and go clearly to the delta positive carbon atom.Your second arrow must start touching the C-X bond and move clearly to the delta negative X atom.Make sure you show the products formed, including the :X - atom which has been substituted. Stewart has been an enthusiastic GCSE, IGCSE, A Level and IB teacher for more than 30 years in the UK as we...

Nucleophilic Substitution Oxidative nucleophilic substitution of hydrogen with tertiary carbanions is a useful method for introducing carbon substituents into heterocyclic nitroarene rings. From: Progress in Heterocyclic Chemistry, 2000 Related terms: • Graphene • Hydrolysis • Polyimide • Oxidation Reaction • Sodium • Oxide • Halide • Graphene Oxide • Nucleophile Nucleophilic substitution of the methylsulfonyl group in position 7 of the [1,2,4]triazolo[2,3- a][1,3,5]triazine 19 ring system has been carried out in order to obtain biologically valuable derivatives ( Scheme 17). The reaction pathway was launched by treatment of derivative 93 with aminoacetaldehyde dimethylacetal in the presence of triethylamine under reflux conditions to give the substitution product 94 which was hydrolyzed by TFA/H 2O to the formylmethylamine 95. This compound was then reacted with an N-arylpiperazine under reductive conditions (by using sodium triacetoxyborohydride) to give the corresponding arylpiperazinylethylamino compound 96. Nucleophilic substitution is one of the major functional group reactions. It is simply the replacement of a leaving-group ligand by an incoming nucleophile ligand. There is no change in the nominal oxidation number at the carbon center of interest. There is also no change in the bond order. Compare this with addition, Section 7.3.1, and elimination, Section 7.5.3. The reactions are shown by the equations in Figure 7.15. The only difference between these two exampl...

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Designing a “good” nucleophilic substitution If you want to do well in this class, there are several things you need to work hard at: Being attentive in class, studying the notes and this textbook (especially before exams), practicing problems, and completing the quizzes and homeworks. As long as you do all of these things then you’re likely to pass (though I can’t give guarantees!). So there are many different factors that can affect your grade. In the same way, the outcome of a reaction (such as nucleophilic substition) depends on many different things – reactants, solvent, etc. When we want to make a chemical in a lab or on a chemical plant, we need to design the reaction so that it works well, and gives a good yield of the product in a reasonable time. The reactants and conditions we use will depend on what we’re trying to do. In this section, we examine what factors will help an S N2 or S N1 reaction be successful. Factors affecting the S N2 reaction As we saw in the previous section, in the S N2 reaction the rate of reaction depends on both the electrophile (usually an alkyl halide) and the nucleophile. In practice, the rates of S N2 reactions vary enormously, and for a practicable procedure we need to make sure that the reaction will happen at a reasonable rate. So what makes for a good S N2 reaction? We need to consider what makes a suitable nucleophile, and what makes a suitable electrophile. Nucleophile strength In • Charge – negatively charged => stronger nucleo...

Consider a general nucleophilic substitution reaction. The second arrow always shows a pair of electrons going toward the leaving group. The best leaving groups "want" those electrons. They don't want to share them with other atoms. Good leaving groups are weak bases. Weak bases have strong conjugate acids. So we can identify weak bases by looking at a #"p"K_"a"# table. Caution: The #"p"K_"a"# value measures the position of an equilibrium. But leaving group ability is based on reaction rates. So although the correlation is good, it's not perfect. In general, the weaker the base, the better the leaving group. Exception: Fluorine is a poor leaving group. F⁻ is a small ion. Its high charge density makes it relatively unpolarizable. The leaving group needs to be polarizable to lower the energy of the transition state. You should never see F⁻ leave in an #"S"_"N"2# reaction. Question: Why is water a good leaving group? Answer #color(white)(ll)#: It isn't! Hydronium ion is the leaving group. Explanation: Consider the equilibrium #"R-OH ⇌ R"^"+" + underbrace("OH"^"-")_color(red)("conj. base of H"_2"O")# Water is a weak acid, so the hydroxide ion is a strong base. It "wants" to use its lone pair electrons to form a covalent bond. Thus, the position of equilibrium lies far to the left. If we protonate the alcohol, we get #"R-"stackrelcolor(blue)(+)("O")"H"_2 ⇌ "R"^"+" + underbrace("OH"_2)_color(red)("conj. base of H"_3"O"^"+")# Water is the conjugate base of hydronium ion, the stro...

SN2 Reaction Mechanism What is S N2 Reaction Mechanism? The S N2 reaction mechanism involves the nucleophilic substitution reaction of the leaving group (which generally consists of halide groups or other electron-withdrawing groups) with a nucleophile in a given organic compound. The rate-determining step of this reaction depends on the interaction between the two species, namely the Table of Contents • • • • S N2 reaction mechanism requires the attack of nucleophile from the back side of the carbon atom. So the product assumes a stereochemical position opposite to the leaving group originally occupied. This is called inversion of configuration. The S N2 reaction is a good example of stereospecific reaction, one in which different stereoisomers react to give different stereoisomers of the product. Also, S N2 reaction is the most common example of Walden inversion where an What is an S N2 Reaction? The S N2 reaction is a nucleophilic substitution reaction where a bond is broken and another is formed synchronously. Two reacting species are involved in the rate determining step of the reaction. The term ‘S N2’ stands for – Substitution Nucleophilic Bimolecular. This type of reaction is also referred to as bimolecular nucleophilic substitution, associative substitution, and interchange mechanism. Some examples of S N2 reactions are illustrated above. The rate of this type of reaction is affected by the following factors: • Unhindered back of the substrate makes the for...

Further Information Related Reactions Nucleophilic Substitution (S N1 S N2) Nucleophilic substitution is the reaction of an electron pair donor (the nucleophile, Nu) with an electron pair acceptor (the electrophile). An sp 3-hybridized electrophile must have a leaving group (X) in order for the reaction to take place. Mechanism of Nucleophilic Substitution The term S N2 means that two molecules are involved in the actual transition state: The departure of the leaving group occurs simultaneously with the backside attack by the nucleophile. The S N2 reaction thus leads to a predictable configuration of the stereocenter - it proceeds with inversion (reversal of the configuration). In the S N1 reaction, a planar carbenium ion is formed first, which then reacts further with the nucleophile. Since the nucleophile is free to attack from either side, this reaction is associated with racemization. In both reactions, the nucleophile competes with the leaving group. Because of this, one must realize what properties a leaving group should have, and what constitutes a good nucleophile. For this reason, it is worthwhile to know which factors will determine whether a reaction follows an S N1 or S N2 pathway. Very good leaving groups, such as triflate, tosylate and mesylate, stabilize an incipient negative charge. The delocalization of this charge is reflected in the fact that these ions are not considered to be nucleophilic. Hydroxide and alkoxide ions are not good leaving groups; howeve...

• العربية • Asturianu • Azərbaycanca • বাংলা • Башҡортса • Català • Čeština • Dansk • Deutsch • Eesti • Español • Euskara • فارسی • Français • Galego • 한국어 • Hrvatski • Bahasa Indonesia • Italiano • עברית • Magyar • Македонски • Bahasa Melayu • Nederlands • 日本語 • Norsk bokmål • Polski • Português • Română • Русский • Shqip • Simple English • Slovenščina • کوردی • Српски / srpski • Srpskohrvatski / српскохрватски • Suomi • Svenska • தமிழ் • Татарча / tatarça • Türkçe • Українська • Tiếng Việt • 中文 "Aromatic substitution" redirects here. For ortho/meta/para patterns, see A substitution reaction (also known as single displacement reaction or single substitution reaction) is a chemical reaction during which one A good example of a substitution reaction is 2) is irradiated, some of the molecules are split into two chlorine 4 and grabs the hydrogen atom to form the electrically neutral HCl. The other radical reforms a covalent bond with the CH 3• to form CH 3Cl ( chlorination of methane by chlorine Nucleophilic substitution [ ] Main article: In organic (and inorganic) chemistry, The most general form for the reaction may be given as Nuc : + R − LG ⟶ R − Nuc + LG : Nucleophilic substitution reactions are commonplace in organic chemistry, and they can be broadly categorized as taking place at a carbon of a saturated Mechanisms [ ] Main articles: Nucleophilic substitutions on aliphatic carbon centers can proceed by two different mechanisms, unimolecular nucleophilic substitution (...

Consider a general nucleophilic substitution reaction. The second arrow always shows a pair of electrons going toward the leaving group. The best leaving groups "want" those electrons. They don't want to share them with other atoms. Good leaving groups are weak bases. Weak bases have strong conjugate acids. So we can identify weak bases by looking at a #"p"K_"a"# table. Caution: The #"p"K_"a"# value measures the position of an equilibrium. But leaving group ability is based on reaction rates. So although the correlation is good, it's not perfect. In general, the weaker the base, the better the leaving group. Exception: Fluorine is a poor leaving group. F⁻ is a small ion. Its high charge density makes it relatively unpolarizable. The leaving group needs to be polarizable to lower the energy of the transition state. You should never see F⁻ leave in an #"S"_"N"2# reaction. Question: Why is water a good leaving group? Answer #color(white)(ll)#: It isn't! Hydronium ion is the leaving group. Explanation: Consider the equilibrium #"R-OH ⇌ R"^"+" + underbrace("OH"^"-")_color(red)("conj. base of H"_2"O")# Water is a weak acid, so the hydroxide ion is a strong base. It "wants" to use its lone pair electrons to form a covalent bond. Thus, the position of equilibrium lies far to the left. If we protonate the alcohol, we get #"R-"stackrelcolor(blue)(+)("O")"H"_2 ⇌ "R"^"+" + underbrace("OH"_2)_color(red)("conj. base of H"_3"O"^"+")# Water is the conjugate base of hydronium ion, the stro...

Further Information Related Reactions Nucleophilic Substitution (S N1 S N2) Nucleophilic substitution is the reaction of an electron pair donor (the nucleophile, Nu) with an electron pair acceptor (the electrophile). An sp 3-hybridized electrophile must have a leaving group (X) in order for the reaction to take place. Mechanism of Nucleophilic Substitution The term S N2 means that two molecules are involved in the actual transition state: The departure of the leaving group occurs simultaneously with the backside attack by the nucleophile. The S N2 reaction thus leads to a predictable configuration of the stereocenter - it proceeds with inversion (reversal of the configuration). In the S N1 reaction, a planar carbenium ion is formed first, which then reacts further with the nucleophile. Since the nucleophile is free to attack from either side, this reaction is associated with racemization. In both reactions, the nucleophile competes with the leaving group. Because of this, one must realize what properties a leaving group should have, and what constitutes a good nucleophile. For this reason, it is worthwhile to know which factors will determine whether a reaction follows an S N1 or S N2 pathway. Very good leaving groups, such as triflate, tosylate and mesylate, stabilize an incipient negative charge. The delocalization of this charge is reflected in the fact that these ions are not considered to be nucleophilic. Hydroxide and alkoxide ions are not good leaving groups; howeve...