DOCSLIB.ORG

The Electrophile

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
The Electrophile The Electrophile 1 ¨ Recall that electrophile means “electron- loving.” ¨ When considering substitution and elimination reactions we must consider the carbon attached to the leaving group. Is it a primary, secondary, or tertiary carbon? Electrophile Type Favors Disfavors Methyl SN2 SN1, E1, E2 Primary SN2, E2 SN1, E1 Secondary SN1, SN2, E1, E2 Resonance Stabilized SN1, SN2 E1, E2 Primary Tertiary SN1, E2, E1 SN2 SN1 and E1 SN2 and E2 least stable most stable least hindered most hindered LG H H LG > > LG < < < H > H H H LG x methyl and primary methyl electrophile Tertiary electrophile is too carbocation too unstable has no β hydrogen. sterically crowded for direct nucleophilic attack. No S 2 to exist. No SN1 or E1 No E2 N The Electrophile: SN1 and E1 Reactions, Carbocation Stability 2 ¨ The first step in a SN1 and E1 reaction is to form a carbocation. If the carbocation is too unstable, then regardless of how good the leaving group is the carbocation will not form. ¨ To determine the stability of a carbocation we must consider inductive and resonance effects What is happening when we say CH3 CH3 CH3 H > > > “inductive” effects? H3C CH3 H3C H H H H H 3o = 3 carbons 2o = 2 carbons 1o = 1 carbon methyl Empty p orbital H hyperconjugation H C C C H H substituted carboncation methyl carboncation ¨ Primary carbocations may be formed if they have resonance stabilization N N O OH H Examining the Leaving Group and Electrophile 3 weak bases= GOOD leaving group Br Cl strong base = BAD leaving group O OH Potential Leaving Groups no SN2 sterically hindered (no SN2) 3 ° Favors S 1, E1, E2 N Br Zaitsev’s Rule: the most Br Cl substituted alkene will be Cl H O OH most stable and therefore 1° Favors S 2, E2 O OH N not sterically hindered the most favored product (allows for E2) 2 ° Favors SN1, SN2, E1, E2 Electrophilic centers Cl H O OH Cl H Br H Br H H H O OH Cl Cl O H Br H H H H H Cl Cl O OH O OH HO most substituted is H H H the E2 product O OH The Leaving Group and the Electrophile: Examples 4 The leaving group here would be Cl-, a good leaving group The electrophile is a secondary electrophile, SN1, SN2, E1, and E2 are all possible Cl The leaving group here would be OH-, a bad 2° C leaving group No reaction is likely to take CH O place here without further modifying the the Haloalkane produced by red algea substrate. HO Br The leaving group here would be Br-, a good leaving group. However, it is attached to an Sp2 carbon, no substitution or elimination reaction will occur here. Practice Question 5 Which substrate will undergo the fastest SN2 reaction? F bad LG ✗ A F 1o electrophile ✓ I good LG ✓ B I 3o electrophile ✗ C OH bad LG ✗ OH 1o electrophile ✓ D Cl good LG ✓ 2o electrophile ✓ Cl The Nucleophile 6 ¨ Recall that nucleophile means “nucleus loving” or “positive-charge loving” ¨ Nucleophiles donate a pair of electrons to an electrophile. (Lewis base!) ¨ When the nucleophile donates a pair of electrons to a proton it is called a Bronsted base or simply a base. The proton is acting like an electrophile. Nucleophile Type Favors Disfavors Strong Nuc/Strong SN2, E2 SN1, E1 Base Strong Nuc/ Weak SN2 SN1, E1, E2 Base Weak Nuc/ Strong E2 SN1, SN2, E1 Base Weak Nuc/Weak Base SN1, E1 SN2, E2 The Nucleophile: Factors That Affect Nucleophilicity and Basicity 7 ¨ How do we know if a nucleophile is acting as a nucleophile or a base? ¤ Consider the following properties: Charge Steric Hindrance Strength of nucleophile/base Electronegativity Solvent The Nucleophile: Charge and Electronegativity 8 ¨ Charge ¤ The greater the electron density on the nucleophile the greater its nucleophilicity ¤ Increased electron density results in an increased desire to donate those electrons; ie: increased nucleophilicity The conjugate base is neutral = SN1, E1 charged = SN2, E2 always a stronger nucleophile ¨ Electronegativity ¤ Electronegativity relates how “tightly” held a pair of electrons are. The more tightly they are held the less the ability for them to be donated is. Electronegativity= Nucleophilicity Electronegativity= Basicity Rank the Following Nucleophiles in Order of Increasing Nucleophilicity (1 being the weakest 5 being the strongest) 9 O OH NH 2 1 3 no charge, less electronegative than weakest oxygen, strongest The Nucleophile: Steric Hindrance 10 ¨ Nucleophilicity decreases with increasing steric bulk ¤ Nucleophiles generally are reacting at electrophilic carbon. The orbitals that participate in the reactions are less accessible than those orbitals on hydrogen. H3C LG !+ bulky nucleophile = E2 H H H H Non-Nucleophilic Bases Li N N N N N ¤ If your nucleophile is bulky then its electrons may not be able to “reach” the antibonding orbitals at the carbon Practice Question 11 ¨ t-butoxide has the following structure. O Based on what you know about nucleophilicity what type of reaction or reactions are favored? E1 or S 1 unlikely as this is a charged A. Both S 1, E1 N N nucleophile (not A or C) B. Both SN2, E2 C. Primarily E1 bulky nucelophiles do not allow for S 2 (not B) D. Primarily E2 N Solvent Effects: The Electrophile 12 Solvent Type Favors Disfavors Polar protic – has hydrogen bound to an electronegative atom Polar Protic SN1, E1 Eg. H2O Polar aprotic – no hydrogens, but still Polar Aprotic SN2, E2 SN1, E1 contains a dipole Eg. CH2Cl2 Non-Polar SN1, SN2, E1, E2 Non-polar – has no dipoles Eg. hexanes, benzene ¨ S 1 and E1 reactions proceed more quickly in polar protic solvents N δ+ ¤ Intermediates are solvated through hydrogen bonding H Oδ- Leaving Group Stabilization H H Carbocation Stabilization O H H Hδ+ H Polar protic solvents favour δ- O O H δ+ SN1 and E1 reactions H δ- O H LG H O δ+ because the intermediates H are solvated H δ- δ+H δO- O H O H H H Solvent effects: The Nucleophile 13 ¨ Nucleophilicity can be affected by solvent ¨ Polar protic solvents cause nucleophilicity to increase going down the periodic table ¨ Polar aprotic solvents cause nucleophilicity to decrease going down the periodic table Solvent Effects: The Nucleophile 14 Polar protic Polar aprotic O O OH OH H H H3C HO water alcohols carboxylic acids H O H H Polar aprotic solvents have dipoles present O H which could interact with the nucleophile, O O O H O H O however the partial positive charge created F H I H H H < O O from the dipole is sterically hindered and O O Na H therefore the nucleophile is unable to interact H H O O O O with these solvent. H H O H Hydrogen bonding between lone pairs and polar protic solvents result Polar aprotic solvents help in the solvolysis of cations which result in “naked” anions in dispersion of negative charge. Lone pairs are tied up in H-bond and Favour SN2, E2 less available to be donated Non-polar solvent O ether hexane Recall that “like dissolves like.” as many nucleophiles are charged or very polar they will not dissolve in non-polar solvents é interaction with solvent = ê nucelophilicity Can you rank the following nucleophiles in order of increasing nucleophilicity? (1 being the weakest 5 being the strongest) 15 O OH H2O O OH H3C O 3 1 5 4 2 Polar protic solvent SH SeH OH 2 3 1 q How would the rate of the reaction change if the solvent was changed from methanol to DMF NaSH protic The protic solvent can interact with the MeOH nucelophile and keep it from reacting Br or with the alkyl bromide. Therefore, DMF DMF aprotic increases the rate of reaction. Temperature Effects 16 ¨ When all else is equal increased temperatures will favor elimination reactions over substitution reactions Temperature Favors Disfavors High E1, E2 SN1, SN2 Low SN1, SN2 E1, E2 ΔG<0 reaction is spontaneous ΔG>0 reaction is non-spontaneous ΔG=0 reaction is in equilibrium ΔG2 ΔG=ΔH-TΔS ΔG1 H Nuc H LG 2 products LG Nuc Δ H G B LG H HB 3 products LG Elimination reaction produces more products, this is favoured in the presence of heat as it increases the universe’s entropy. Mind Map 17 Practice Question 18 ¨ What is the most likely reaction to occur under the following conditions? ¨ What is the most likely product of the following reaction. H C A 3 O Br CH3O HO Br heat 1. LG? OH or Br B Br is a better LG HO OCH3 2. Electrophile? 3o Which product is formed? C or D? SN1, E1, E2 possible 3. Nucleophile? Strong Recall Zaitsev’s Rule! C The most stable product is C. favours SN2, E2 HO 4. Solvent? N.A. 5. Temperature? Yes eliminations preferred D Therefore, E2 reaction occurs (not A or B) HO Substitution and Elimination Reactions 19 O H O Cl H O Acetone O Room Temp Stereochemistry is inverted 1. LG: Cl 2. Electrophile: 2o, Favours SN1, SN2, E1, E2 3. Nucleophile: Charged, Favours SN2, E2 4: Solvent: Polar Aprotic, Favours SN2, E2 5. Temperature: Room Temp, Favours SN2 so SN2 Reaction H H H Br Br H N DMSO Heat H H 1. LG: Br N 2. Electrophile: 3o, Favours SN1, E1, E2 heat 3. Nucleophile: Neutral but strong and Bulky, Favours E2 4: Solvent: Polar Aprotic, Favours SN2, E2 5. Temperature: Heat, Favours E2 heat so E2 Reaction 20 H H Br O O H H H2O E1 product: most SN1 products: mixture of stubstituded alkene stereochemistry 1.
Load more

Recommended publications
  • Products from Reactions of Carbon Nucleophiles and Carbon
    14C synthesis strategies, Chem 315/316 / Beauchamp 1 Products from reactions of carbon nucleophiles and carbon electrophiles used in the 14C Game and our course: Carbon and hydrogen nucleophiles Ph R Ph Al H N R Li R (MgBr) P Li AlH R Cu Li Na CN RCC Na Ph 4 Li Carbon 2 H C R organolithium organolithium cyanide acetylides 2 ylid Na BH4 diisobutylaluminium lithium diisopropy- electrophiles cuprates (LAH) o reagents reagents Wittig reagents hydride (DIBAH) amide (LDA), -78 C H C Br 3 not useful not useful 2 RX coupling nitrilesalkynes not useful alkyls alkyls not useful methyl RX reaction R Br not useful not useful 2 RX coupling nitriles alkynes not useful alkyls alkyls not useful primary RX reaction R 2 RX coupling nitriles alkyls not useful E2 not useful alkyls not useful not useful reaction R Br secondary RX O 1o ROH 1o ROH 1o ROH 1o ROH not useful 1o ROH o not useful not useful 1o ROH 1 ROH ethylene oxide nitriles alkynes O o o o o o o 2 ROH 2 ROH 2 ROH 2 ROH 2o ROH 2 ROH 2 ROH not useful not useful E2, make nitriles alkynes allylic alcohols propylene oxide O o 3 ROH 3o ROH o 3o ROH o not useful o 3o ROH not useful E2, make 3 ROH 3 ROH 3 ROH allylic alcohols nitriles alkynes isobutylene oxide O o o specific methanol methanol C 1 ROH 1 ROH not used cyanohydrin 1o ROH not useful not useful in our course alkenes H H alkynes methanal O specific o enolate o o cyanohydrin o 1 ROH o C 2 ROH 2 ROH not useful 2 ROH alkenes 1 ROH not useful chemistry R H alkynes simple aldehydes O cyanohydrin o unless specific o enolate C 3 ROH 3o ROH o 2o ROH
    [Show full text]
  • Solvent Effects on Structure and Reaction Mechanism: a Theoretical Study of [2 + 2] Polar Cycloaddition Between Ketene and Imine
    J. Phys. Chem. B 1998, 102, 7877-7881 7877 Solvent Effects on Structure and Reaction Mechanism: A Theoretical Study of [2 + 2] Polar Cycloaddition between Ketene and Imine Thanh N. Truong Henry Eyring Center for Theoretical Chemistry, Department of Chemistry, UniVersity of Utah, Salt Lake City, Utah 84112 ReceiVed: March 25, 1998; In Final Form: July 17, 1998 The effects of aqueous solvent on structures and mechanism of the [2 + 2] cycloaddition between ketene and imine were investigated by using correlated MP2 and MP4 levels of ab initio molecular orbital theory in conjunction with the dielectric continuum Generalized Conductor-like Screening Model (GCOSMO) for solvation. We found that reactions in the gas phase and in aqueous solution have very different topology on the free energy surfaces but have similar characteristic motion along the reaction coordinate. First, it involves formation of a planar trans-conformation zwitterionic complex, then a rotation of the two moieties to form the cycloaddition product. Aqueous solvent significantly stabilizes the zwitterionic complex, consequently changing the topology of the free energy surface from a gas-phase single barrier (one-step) process to a double barrier (two-step) one with a stable intermediate. Electrostatic solvent-solute interaction was found to be the dominant factor in lowering the activation energy by 4.5 kcal/mol. The present calculated results are consistent with previous experimental data. Introduction Lim and Jorgensen have also carried out free energy perturbation (FEP) theory simulations with accurate force field that includes + [2 2] cycloaddition reactions are useful synthetic routes to solute polarization effects and found even much larger solvent - formation of four-membered rings.
    [Show full text]
  • Solvents and Solvent E¤Ects in Organic Chemistry
    Contents 1 Introduction ......................................................... 1 2 Solute-Solvent Interactions ........................................... 7 2.1 Solutions . .......................................................... 7 2.2 Intermolecular Forces . ............................................ 12 2.2.1 Ion-Dipole Forces . ................................................. 13 2.2.2 Dipole-Dipole Forces................................................ 14 2.2.3 Dipole-Induced Dipole Forces ....................................... 15 2.2.4 Instantaneous Dipole-Induced Dipole Forces . ...................... 16 2.2.5 Hydrogen Bonding . ................................................. 17 2.2.6 Electron-Pair Donor/Electron-Pair Acceptor Interactions (EPD/EPA Interactions) . ..................................................... 23 2.2.7 Solvophobic Interactions ............................................ 31 2.3 Solvation . .......................................................... 34 2.4 Preferential Solvation................................................ 43 2.5 Micellar Solvation (Solubilization) ................................... 48 2.6 Ionization and Dissociation . ........................................ 52 3 Classification of Solvents ............................................. 65 3.1 Classification of Solvents according to Chemical Constitution ......... 65 3.2 Classification of Solvents using Physical Constants . .................. 75 3.3 Classification of Solvents in Terms of Acid-Base Behaviour. ......... 88 3.3.1 Brønsted-Lowry
    [Show full text]
  • Chapter 7, Haloalkanes, Properties and Substitution Reactions of Haloalkanes Table of Contents 1
    Chapter 7, Haloalkanes, Properties and Substitution Reactions of Haloalkanes Table of Contents 1. Alkyl Halides (Haloalkane) 2. Nucleophilic Substitution Reactions (SNX, X=1 or 2) 3. Nucleophiles (Acid-Base Chemistry, pka) 4. Leaving Groups (Acid-Base Chemistry, pka) 5. Kinetics of a Nucleophilic Substitution Reaction: An SN2 Reaction 6. A Mechanism for the SN2 Reaction 7. The Stereochemistry of SN2 Reactions 8. A Mechanism for the SN1 Reaction 9. Carbocations, SN1, E1 10. Stereochemistry of SN1 Reactions 11. Factors Affecting the Rates of SN1 and SN2 Reactions 12. --Eliminations, E1 and E2 13. E2 and E1 mechanisms and product predictions In this chapter we will consider: What groups can be replaced (i.e., substituted) or eliminated The various mechanisms by which such processes occur The conditions that can promote such reactions Alkyl Halides (Haloalkane) An alkyl halide has a halogen atom bonded to an sp3-hybridized (tetrahedral) carbon atom The carbon–chlorine and carbon– bromine bonds are polarized because the halogen is more electronegative than carbon The carbon-iodine bond do not have a per- manent dipole, the bond is easily polarizable Iodine is a good leaving group due to its polarizability, i.e. its ability to stabilize a charge due to its large atomic size Generally, a carbon-halogen bond is polar with a partial positive () charge on the carbon and partial negative () charge on the halogen C X X = Cl, Br, I Different Types of Organic Halides Alkyl halides (haloalkanes) sp3-hybridized Attached to Attached to Attached
    [Show full text]
  • Reactions of Benzene & Its Derivatives
    Organic Lecture Series ReactionsReactions ofof BenzeneBenzene && ItsIts DerivativesDerivatives Chapter 22 1 Organic Lecture Series Reactions of Benzene The most characteristic reaction of aromatic compounds is substitution at a ring carbon: Halogenation: FeCl3 H + Cl2 Cl + HCl Chlorobenzene Nitration: H2 SO4 HNO+ HNO3 2 + H2 O Nitrobenzene 2 Organic Lecture Series Reactions of Benzene Sulfonation: H 2 SO4 HSO+ SO3 3 H Benzenesulfonic acid Alkylation: AlX3 H + RX R + HX An alkylbenzene Acylation: O O AlX H + RCX 3 CR + HX An acylbenzene 3 Organic Lecture Series Carbon-Carbon Bond Formations: R RCl AlCl3 Arenes Alkylbenzenes 4 Organic Lecture Series Electrophilic Aromatic Substitution • Electrophilic aromatic substitution: a reaction in which a hydrogen atom of an aromatic ring is replaced by an electrophile H E + + + E + H • In this section: – several common types of electrophiles – how each is generated – the mechanism by which each replaces hydrogen 5 Organic Lecture Series EAS: General Mechanism • A general mechanism slow, rate + determining H Step 1: H + E+ E El e ctro - Resonance-stabilized phile cation intermediate + H fast Step 2: E + H+ E • Key question: What is the electrophile and how is it generated? 6 Organic Lecture Series + + 7 Organic Lecture Series Chlorination Step 1: formation of a chloronium ion Cl Cl + + - - Cl Cl+ Fe Cl Cl Cl Fe Cl Cl Fe Cl4 Cl Cl Chlorine Ferric chloride A molecular complex An ion pair (a Lewis (a Lewis with a positive charge containing a base) acid) on ch lorine ch loronium ion Step 2: attack of
    [Show full text]
  • The Role of Hydrogen Bonding in Paracetamol–Solvent and Paracetamol–Hydrogel Matrix Interactions
    materials Article The Role of Hydrogen Bonding in Paracetamol–Solvent and Paracetamol–Hydrogel Matrix Interactions Marta Miotke-Wasilczyk *, Marek Józefowicz * , Justyna Strankowska and Jerzy Kwela Insitute of Experimental Physics, Faculty of Mathematics, Physics and Informatics, University of Gda´nsk, Wita Stwosza 57, 80-308 Gda´nsk,Poland; [email protected] (J.S.); [email protected] (J.K.) * Correspondence: [email protected] (M.M.-W.); [email protected] (M.J.) Abstract: The photophysical and photochemical properties of antipyretic drug – paracetamol (PAR) and its two analogs with different substituents (acetanilide (ACT) and N-ethylaniline (NEA)) in 14 solvents of different polarity were investigated by the use of steady–state spectroscopic technique and quantum–chemical calculations. As expected, the results show that the spectroscopic behavior of PAR, ACT, and NEA is highly dependent on the nature of the solute–solvent interactions (non- specific (dipole-dipole) and specific (hydrogen bonding)). To characterize these interactions, the multiparameter regression analysis proposed by Catalán was used. In order to obtain a deeper insight into the electronic and optical properties of the studied molecules, the difference of the dipole moments of a molecule in the ground and excited state were determined using the theory proposed by Lippert, Mataga, McRae, Bakhshiev, Bilot, and Kawski. Additionally, the influence of the solute polarizability on the determined dipole moments was discussed. The results of the solvatochromic studies were related to the observations of the release kinetics of PAR, ACT, and NEA from polyurethane hydrogels. The release kinetics was analyzed using the Korsmayer-Peppas and Hopfenberg models.
    [Show full text]
  • 101 Lime Solvent
    Sure Klean® CLEANING & PROTECTIVE TREATMENTS 101 Lime Solvent Sure Klean® 101 Lime Solvent is a concentrated acidic cleaner for dark-colored brick and tile REGULATORY COMPLIANCE surfaces which are not subject to metallic oxidation. VOC Compliance Safely removes excess mortar and construction dirt. Sure Klean® 101 Lime Solvent is compliant with all national, state and district VOC regulations. ADVANTAGES • Removes construction dirt and excess mortar with TYPICAL TECHNICAL DATA simple cold water rinse. Clear, brown liquid • Removes efflorescence from new brick and new FORM Pungent odor stone construction. SPECIFIC GRAVITY 1.12 • Safer than muriatic acid on colored mortar and dark-colored new masonry surfaces. pH 0.50 @ 1:6 dilution • Proven effective since 1954. WT/GAL 9.39 lbs Limitations ACTIVE CONTENT not applicable • Not generally effective in removal of atmospheric TOTAL SOLIDS not applicable stains and black carbon found on older masonry VOC CONTENT not applicable surfaces. Use the appropriate Sure Klean® FLASH POINT not applicable restoration cleaner to remove atmospheric staining from older masonry surfaces. FREEZE POINT <–22° F (<–30° C) • Not for use on polished natural stone. SHELF LIFE 3 years in tightly sealed, • Not for use on treated low-E glass; acrylic and unopened container polycarbonate sheet glazing; and glazing with surface-applied reflective, metallic or other synthetic coatings and films. SAFETY INFORMATION Always read full label and SDS for precautionary instructions before use. Use appropriate safety equipment and job site controls during application and handling. 24-Hour Emergency Information: INFOTRAC at 800-535-5053 Product Data Sheet • Page 1 of 4 • Item #10010 – 102715 • ©2015 PROSOCO, Inc.
    [Show full text]
  • Diastereoisomers As Probes for Solvent Reorganizational Effects On
    Chemical Physics 324 (2006) 8–25 www.elsevier.com/locate/chemphys Diastereoisomers as probes for solvent reorganizational effects on IVCT in dinuclear ruthenium complexes Deanna M. DÕAlessandro, F. Richard Keene * Department of Chemistry, School of Pharmacy and Molecular Sciences, James Cook University, Townsville, Qld. 4811, Australia Received 19 June 2005; accepted 1 September 2005 Available online 3 October 2005 Abstract 5+ 0 0 IVCT solvatochromism studies on the meso and rac diastereoisomers of [{Ru(bpy)2}2(l-bpm)] (bpy = 2,2 -bipyridine; bpm = 2,2 - bipyrimidine) in a homologous series of nitrile solvents revealed that stereochemically directed specific solvent effects in the first solvation shell dominated the outer sphere contribution to the reorganizational energy for intramolecular electron transfer. Further, solvent pro- portion experiments in acetonitrile/propionitrile mixtures indicated that the magnitude and direction of the specific effect was dependent on the relative abilities of discrete solvent molecules to penetrate the clefts between the planes of the terminal polypyridyl ligands. In particular, the specific effects were dependent on the dimensionality of the clefts, and the number, size, orientation and location of the solvent dipoles within the interior and exterior clefts. 5+ 5+ IVCT solvatochromism studies on the diastereoisomeric forms of [{Ru(bpy)2}2(l-dbneil)] and [{Ru(pp)2}2(l-bpm)] {dbneil = dibenzoeilatin; pp = substituted derivatives of 2,20-bipyridine and 1,10-phenanthroline} revealed that the subtle and systematic changes in the nature of the clefts by the variation of the bridging ligand, and the judicious positioning of substituents on the terminal ligands, profoundly influenced the magnitude of the reorganizational energy contribution to the electron transfer barrier.
    [Show full text]
  • Chapter 20 the Carbonyl Can Be an Electrophile, It Can Be Attacked. It Can Occur Under Basic Or Acidic Conditions
    Chapter 20 The carbonyl can be an electrophile, it can be attacked. It can occur under basic or acidic conditions. Basic Conditions: H O 1. Nu- O 2. H2O workup Nu Nu: HOH O : Nu Acidic Conditions: H+ H O : 1. H+, Nu: O Nu H + O OH Nu Nu: Hydride reductions. Basic conditions, H- is the nucleophile Ketones and aldehydes react w/ LiAlH4. H O 1. LiAlH4 O 2. H2O workup - H H: HOH O : H Esters and acid chlorides react w/ LiAlH4. H O 1. LiAlH4 O 2. H O workup OMe 2 H - H H: HOH O : O O : OMe H H H - H H: There are many sources of hydride with various reactivities Hydride Aldehyde Ketone Ester Amide Carboxyllic Acid Donors acid/ acid salt halide LiAlH4 Alcohol Alcohol Alcohol Amine Alcohol Alcohol LiAlH(OtBu)3 Alcohol Alcohol Alcohol - (too slow) N.R. Aldehyde NaBH4 Alcohol Alcohol N.R. N.R. N.R. ? NaBH3CN Alcohol N.R. N.R. N.R. N.R. ? DIBAL-H Alcohol Alcohol Aldehyde * Aldehyde* Alcohol ? * Stoichiometry must be carefully controlled. H2, Pd/C reacts preferentially with carbon-carbon double bonds. Carbon Nucleophiles: - Both of the following create reagents that act like CH3 . EtBr + 2Li →EtLi + LiBr EtBr + Mg → EtMgBr Alkyne nucleophiles. - + CH3C≡CH + NaNH2→ CH3C≡C: Na + NH3 - + CH3C≡CH + CH3Li → CH3C≡C: Li + CH4↑ CH3C≡CH + CH3MgBr → CH3C≡CMgBr + CH4↑ Ketones and aldehydes react w/ these carbon nucleophiles. H O 1. H3C CCMgBr O 2. H2O workup - C CH3CC: C CH HOH 3 O : Esters and acid chlorides react w/ these carbon nucleophiles.
    [Show full text]
  • Solvent Effects on the Thermodynamic Functions of Dissociation of Anilines and Phenols
    University of Wollongong Research Online University of Wollongong Thesis Collection 1954-2016 University of Wollongong Thesis Collections 1982 Solvent effects on the thermodynamic functions of dissociation of anilines and phenols Barkat A. Khawaja University of Wollongong Follow this and additional works at: https://ro.uow.edu.au/theses University of Wollongong Copyright Warning You may print or download ONE copy of this document for the purpose of your own research or study. The University does not authorise you to copy, communicate or otherwise make available electronically to any other person any copyright material contained on this site. You are reminded of the following: This work is copyright. Apart from any use permitted under the Copyright Act 1968, no part of this work may be reproduced by any process, nor may any other exclusive right be exercised, without the permission of the author. Copyright owners are entitled to take legal action against persons who infringe their copyright. A reproduction of material that is protected by copyright may be a copyright infringement. A court may impose penalties and award damages in relation to offences and infringements relating to copyright material. Higher penalties may apply, and higher damages may be awarded, for offences and infringements involving the conversion of material into digital or electronic form. Unless otherwise indicated, the views expressed in this thesis are those of the author and do not necessarily represent the views of the University of Wollongong. Recommended Citation Khawaja, Barkat A., Solvent effects on the thermodynamic functions of dissociation of anilines and phenols, Master of Science thesis, Department of Chemistry, University of Wollongong, 1982.
    [Show full text]
  • Solvatochromism, Solvents, Polarity, Pomiferin, Absorption
    Physical Chemistry 2016, 6(2): 33-38 DOI: 10.5923/j.pc.20160602.01 Study in the Solvent Polarity Effects on Solvatochromic Behaviour of Pomiferin Erol Tasal1, Ebru Gungor2,*, Tayyar Gungor2 1Physics Department, Eskisehir Osmangazi University, Eskisehir, Turkey 2Energy Systems Engineering Department, Mehmet Akif Ersoy University, Burdur, Turkey Abstract Solvent polarity is very important considering the coulombic and dispersive interactions between the charge distribution in the solubility and the polarizability of the solvent. Therefore, the solvatochromic properties of pomiferin molecule in solvents of different polarities has been investigated. So, the electronic absorption of pomiferin molecule at room temperature was analyzed by using some physical parameters such as refractive index, dielectric constant, Kamlet–Taft parameters α (hydrogen bond donating ability) and β (hydrogen bond accepting ability). The absorption spectra were decomposed by using multiple peak analysis. It was obtained that some solvents indicated a good linearity for hydrogen-bond acceptor basicity parameter, refractive index and dielectric constant with respect to wavenumber. This showed that the hydrogen-bond acceptor basicity parameter is the most important parameter for both dissociation and complex formation reactions, and the hydrogen bonding acceptor ability and the induction-dispersive forces of solvent molecules have caused the bathochromic shift in absorption maxima of pomiferin molecule. Keywords Solvatochromism, Solvents, Polarity, Pomiferin, Absorption increased collagen expression in ex vivo hair follicles [23]. 1. Introduction Ultraviolet–visible (UV-Vis) spectroscopy is proven as a convenient technique to study electronic absorption Pomiferin molecule is known to exhibit solvatochromic properties of the molecule and to understand the solvent behavior and find various pharmaceutical applications.
    [Show full text]
  • Solvent-Tunable Binding of Hydrophilic and Hydrophobic Guests by Amphiphilic Molecular Baskets Yan Zhao Iowa State University, [email protected]
    Chemistry Publications Chemistry 8-2005 Solvent-Tunable Binding of Hydrophilic and Hydrophobic Guests by Amphiphilic Molecular Baskets Yan Zhao Iowa State University, [email protected] Eui-Hyun Ryu Iowa State University Follow this and additional works at: http://lib.dr.iastate.edu/chem_pubs Part of the Chemistry Commons The ompc lete bibliographic information for this item can be found at http://lib.dr.iastate.edu/ chem_pubs/197. For information on how to cite this item, please visit http://lib.dr.iastate.edu/ howtocite.html. This Article is brought to you for free and open access by the Chemistry at Iowa State University Digital Repository. It has been accepted for inclusion in Chemistry Publications by an authorized administrator of Iowa State University Digital Repository. For more information, please contact [email protected]. Solvent-Tunable Binding of Hydrophilic and Hydrophobic Guests by Amphiphilic Molecular Baskets Abstract Responsive amphiphilic molecular baskets were obtained by attaching four facially amphiphilic cholate groups to a tetraaminocalixarene scaffold. Their binding properties can be switched by solvent changes. In nonpolar solvents, the molecules utilize the hydrophilic faces of the cholates to bind hydrophilic molecules such as glucose derivatives. In polar solvents, the molecules employ the hydrophobic faces of the cholates to bind hydrophobic guests. A water-soluble basket can bind polycyclic aromatic hydrocarbons including anthracene, pyrene, and perylene. The binding free energy (−ΔG) ranges from 5 to 8 kcal/mol and is directly proportional to the surface area of the aromatic hosts. Binding of both hydrophilic and hydrophobic guests is driven by solvophobic interactions. Disciplines Chemistry Comments Reprinted (adapted) with permission from Journal of Organic Chemistry 70 (2005): 7585, doi:10.1021/ jo051127f.
    [Show full text]