pyrrole pyridine aniline basicity

Problem Set n

Rank the compounds in each group in order ot increasing basicity NH2 NH2 a NH3 NH2 d C6H5NH2 (C6H5)2NH Which compound in each pair is the stronger base? (CH3CH2)2NH or (CICH2CH2)2NH a b (CH3CH2)2NH or or (CH3)3N c d Give a systematic or common name for each compound CH2CH3 NH2 a CH3NHCH2CH2CH2CH3 NH2 NH2 CH2CH2CH3 g (CH3CH2CH2)3N

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Aromatics at University of Nottingham

Hammett constants (substituent constants - σ p) Substituent constant pKa of benzoic acid - pKa of benzoic acid with substituent at para (meta - σ m but ortho includes steric effects so no Hammett) so ERG are negative EWG positive Benzoic acid can't delocalize charge of anion into the ring Reaction constant - log (k X /k H) = ρσ p (log of ratios of reaction constants equals reaction

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pKa Chart 1 2 conjugate acid conjugate base conjugate acid

pyridine 5 2 pKa Chart conjugate acid conjugate base conjugate acid conjugate base s t r o n g e s t a c i d s w e a k e s t b a s e s hydrogen sulfide 1 2 (bicarbonate) hydrochloric acid -7 carbocations -3 O O OH H HN H H HCN NH2 O H H H3C N H H H S H HCO3-NH H H CN S CO3-2 NH O O O H3CN H H O H H O H O H HH O O CCH N R H H O O H H H O OH O O

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Boc

General The formation of Boc-protected amines and amino acids is conducted under either aqueous or anhydrous conditions by reaction with a base and the anhydride Boc 2 O Active esters and other derivatives such as Boc-ONH 2 and Boc-N 3 can also be used The Boc group is stable towards most nucleophiles and bases

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B Sc Semester III Chem – 201 [Organic Chemistry]

substitution of Pyrrole Furan and Thiophene reactivity and orientation of electrophilic substitution reactions (ESR) in five membered heterocycles (Pyrrole Furan and Thiophene) Structure of Pyridine Electrophilic and Nucleophilic substitution reactions of pyridine Basicity of pyridine [B] -dicarbonyl compounds [Marks -6]

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Title page doc

protonation Moreover pyrrole is a weaker base than pyridine and even than aniline in which lone pair on the nitrogen atom is involved in the resonance and not essentially contributes to the aromatic sexlet The protonation of pyrrole at nitrogen or C2 or C3 atom of the ring reduces its basicity and destroys its aromaticity However C- and N-

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Introduction

E g basicity of pyrrole vs pyridine basicity of aniline vs cyclohexylamine 34 c) Antiaromaticity Antiaromatic compounds are highly unstable and generally cannot be formed Molecules will try and avoid antiaromatic situations 35 PROBLEMS 36 7) Tautomers and Equilibrium

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C

3 Both pyridine and pyrrole are aromatic molecules Ho do you account for the fact that pyrrole is less basic than pyridine? (Hint consider the availability of the lone pair of electrons on nitrogen for protonation in each of the molecules) Learning activities : 1 Draw the molecular orbital pictures for benzene pyridine

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CHEMISTRY – PG 2016 Final

CHEMISTRY – PG 2016 Final 1) What is the empirical formula of a compound that contains 72g carbon 18g hydrogen and 192g oxygen? (The masses of H C and O are 1 12 and 16) A CH4O4 B CHO C CH3O2 D CH4O2 2) What kind of orbitals do the nonbonding electrons of the oxygen in an alcohol occupy? A They occupy s orbitals

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Chapter 18: Aldehydes Ketones

Chapter 18: Aldehydes Ketones General Discussion: Aldehydes ketones are examples of carbonyl compounds: O pyridine 5 25 *pyrrole –1 0 piperidine 11 12 The Effect of Resonance on Basicity: Aniline Vs Protonated aniline Pyrrole Vs Protonated pyrrole 28 The Effect of Hybridization on Basicity: Aniline Vs

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Aromatization — Wikipedia Republished // WIKI 2

Aromatization is a chemical reaction in which an aromatic system is formed It can also refer to the production of a new aromatic moiety in a molecule which is already aromatic Theoretically this can be achieved by dehydrogenation of existing cyclic compounds (such as in converting cyclohexane into benzene) or by formation of new cyclic system (such as in the cyclotrimerization of acetylene

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Chapter 19 Amines

Basicity of Amines Lone pair of electrons on nitrogen can accept a proton from an acid Aqueous solutions are basic to litmus Ammonia pK b = 4 74 Alkyl amines are usually stronger bases than ammonia Increasing the number of alkyl groups decreases solvation of ion so 2 and 3 amines are similar to 1 amines in basicity

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Lecture Notes Chem 51C S King

Lecture Notes Chem 51C S King Chapter 25 Amines Amines are widely found in nature Many plants synthesize complex amines called alkaloids some of which have medicinal or poisonous properties Some famous amines: H O HO NH2 CH3 HN CH3 C3 HN H OH HN CH3 CH3 HN CH3 O O CH3 N N O HO HO OH HN CH3 HO HO NH2 OH HN CH2CH3 CH3 CF3 NH2 CH3 CH3 HN C O

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24 4: Basicity of Amines

The aniline pyridine and pyrrole examples are good models for predicting the reactivity of nitrogen atoms in more complex ring systems (a huge diversity of which are found in nature) The tryptophan side chain for example contains a non-basic 'pyrrole-like' nitrogen while adenine (a

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Chapter 23 Review Questions

The para nitro group of 4-nitroaniline is a resonance electron withdrawing substitutent thereby reducing the electron density of the nitrogen and lowering its basicity relative to aniline The 4-methyl group of toluidine is a weak inductive electron donating group thereby increasing the electron density of the nitrogen and increasing its

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KAKATIYA UNIVERSITY

Preparation of furan Pyrrole and thiophene from 1 4-dicarbonyl compounds only Paul-Knorr synthesis structure of pyridine Basicity – Aromaticity – Comparision with pyrrole – one method of preparation and properties – Reactivity towards Nucleophilic substitution reaction –Chichibabin reaction 3 Carbohydrates: (6 h)

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C:Usersmrh70950DocumentsMy FilesWordPerfect DocumentsOrgo

aniline pyrrole pyridine II Properties A display hydrogen bonding B spectroscopy 1 IR a 1E: 2 N–H stretches 3500 - 3300 cm-1 b 2E: 1 N–H stretche 3500 - 3300 cm-1 c 3E: no N–H stretch 2 NMR a NH can appear anywhere and is exchangeable C basicity 1 are weak bases can react with acids to form ammonium salts 207

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