Organic Chemistry Test 2 Study Outline
Organic Chemistry Test 2 Study Outline CHEM 333 001
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CHEM 321 001
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This 16 page Study Guide was uploaded by Hayley on Sunday October 18, 2015. The Study Guide belongs to CHEM 333 001 at University of South Carolina taught by John Lavigne in Summer 2015. Since its upload, it has received 106 views. For similar materials see Organic Chemistry I in Chemistry at University of South Carolina.
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Date Created: 10/18/15
mganic Chemistry Test 2 Outline What to study List given in class RXN mechanisms LALB AcidBase o Pka o Equilibria 0 Factors that in uence pka 5 of them Conformations o Acyclic I Newman projections 0 Cyclic I Astrain substituents Stereochemistry o Chiral achiral o EnantiomersDiastereomers o R S assignments CIP Review IHD formula 2n2H in formula2 where n of C Pre xes of Carbons o Meth Eth m1 mp o Deca Functional Groups C and H atoms 0 AlkaneSingle bond 0 Alkene double bond 0 Alkynes triple bond OOOOOOO pKa Values 0 Alkane 50 Alkene 4246 Alkyne 2226 Ketone 1820 Amine 3842 Alcohol 1618 Phenol 911 Ammonium 911 CH3C02H Carboxylic Acid 45 Hydronium 174 Protonated oxygen alcohol ketone aldehyde ester 2ish HCl 6 H1 9 Large pKa means it s a weak acid strong conjugate base AcidBase Reactions All about stability of the charged species What atom is the charge on Equilibrium lies towards the weaker acid How to push rxn towards product Excess reactant o LeChatlier Principle How to pull rxn towards product Remove product 0 LeChatlier Principle 0 Distillation and Precipitation For resonance you need morbitals Looks like a gure 8 Factors that impact pKa stability of a charged species Electronegativity Size polarizability Resonance Induction sigma bonds Hybridization Two trends 9 same row electronegatiVity and same column size 1 Rows ElectronegatiVity Ka Electronegativity CH3OH 9 CH3O39 H 16 most CH3NH2 9 CH3NH39 H 38 CH3CH3 9 CH3CH239 H 50 least more electronegatlve atoms are the more ac1d1c H more electronegative atoms are the more acidic the conjugate acid is because it wants electrons which makes it a more stable anion Here trend but size does 2 ColumnSize Ka Electronegativity Size HF 9 F39 2 More Small HCl 9 Cl39 6 HBr 9 Br39 8 HI 9 l39 9 Least Large For example F39 9 electrons owned l electron added 10 electrons a smaller atom l39 53 electrons owned 1 electron added 54 electrons a larger atom The uorine has a bigger change than the Iodide A 1011 change versus a gt2 change Therefore HF is a weaker acid If acidity were explained by electronegativity then HF would be more acidic than HI since I is more stable than F then H1 is the stronger acid because H1 is more likely to give up its proton compared to HF LaVigne said not to worry about going in between rows and columns It s like comparing apples to stea Sum up of these two oints compares atoms in same is for comparing atoms in the same 3 Resonance 313 system Delocalizing TE electrons spread out electrons More acidic because it s delocalizing TE electrons Example pKa 16 CH3CH20H 9 CH3CH2039 H 45 CH3COOH 9 CH3COO39 H 4 Induction 0 system Not as affective at spreading out electron density out as resonance Polarized bonds ls distance dependent 0 Further away less force is exerted in charge I Example magnets Think of it as sucking electron density through sigma system pKa 45 CH3COOH 9 CH3COO39 28 ClCHZCOOH 9 ClCH2COO39 Why is the 2nd one less than 45 Because of same resonance and same atoms not EN size A dipole is created Cl 5 Hybridization of S character makes a difference pKa Hybridization S character H3CCH2 50 Sp3 25 H3CCH2 40 Sp2 33 H3CECH2 25 Sp 50 more S charactercloser to nucleus positive Source Lewis Base LB Lone pairs pi bonds Sink Lewis acid LA H C B Al Polarized Bond Think All orianic chemist rxn s are acidbase rxn Sum up of all the factors Recai from Mondai l Electronegativity for ROWS more electronegative more acidic increase electronegativity increase acidity lower pKa 2Size of atom Columns Charge increase in size increase in acidity lower pKa 3 Resonance must have P orbitals not distance dependent Induction sigma pathway delocalization of electrons between nuclei Less affective at electron delocalization compared to resonance Polarizationdipole Distance dependent Electron withdrawing groups EWG o Stabilizes negative charge 0 ClBrI EN vs CH Electron donating groups EDG o Stabilizes cations positive charge 5 Hybridization A of S character makes a difference Chapter 4 Isomers Constitutional same molecular formula different connectivity conformational same molecular form and same connectivity but different orientation in space 0 lnterconvert by simple bond rotation Coplanar in plane of paper exclude wedge and lines Different orientation in space 9different 3D structure Newman Projection Looking down at carboncarbon bonds 0 Staggered far away 0 Eclipse Typical rotation step 60 HCH angle1095 Staggered has a lower energy vs eclipse 0 In a eclipse repulsion of electrons is present so they want to get away from each other more energy being used 0 Torsional strain HCH angle deviates from preferred It s different so there an increase in energy Rotational Itinerary ALKANES as energy increases Eclipse 0 120 240 360 Staggered 60 180 300 Dihedral Bond Angle energy difference is l kcalmol What about double bonds They don t stagger and eclipse as much so don t worry about them Conformations Molecules can be exible They can bend twist etc Predicting how molecules bend twist etc in space Can be in or positions Why is it important Certain reactions can only take place during a certain conformation Two types of drawings 0 Newman Projections 0 Chair Newman Proiections 0 Need to know I Wedge 9coming towards you I Dash 9Going away from you I Used to clearly see both groups from a 3D perspective I Looking down a carboncarbon bond and 3 groups attached to each carbon 0 How to read this Newman projection I a front carbon I b back carbon I Me methyl group I Central point Cl F and Me 9 1st carbon I Circle back carbon and it s elements is If Ci I L i y if a f nilV I unk M 27 Groups can be staggered can see all groups or eclipsed can t see back groups Cyclic Alkanes C3 Cyclopropane Always eclipsed 0 Has a high torsional strain Always in same plane Angle strain deviation from preferred bond angle 0 Bond angle CCC I Want 1095 I Have 60 The sigma bonds in Cyclopropane are bent and have a weird overlap They are referred to as banana bonds 0 In terms of reactivity these bonds are more reactive less stable than normal sigma bonds C4 Bond angle 0 Want 1095 Have 90 Twist it and it reduces torsional strain but increases angle strain Eclipsed Butter y conformation OOOO reduce s in rmse 5 4 have sona Wash shall n 8H a1 0 C5 Cyclopentane Bond angle 0 Have 180 0 Want 1095 Those degrees are close together small angle strain eclipsed Has a high torsional strain atplanar because everything is eclipsed but twisting will reduce it Envelope conformation C6 Cyclohexane staggered Bond angle 0 Have 120 0 Want 1095 Chair conformation Chair Conformation continue C6 A lot of exibility stability Axial Equatorial Bond angle 110 Substituents don t want to be axial During a chair ip axial becomes equatorial equatorial becomes axial V i39 x i It I mFm39 I E sz fmaak A a These are not the same energy If you put anything bigger than hydrogen in axial position it will increase the energy of that conformation vertical up down axial horizontal across equatorial E xing l 5 quot r r if 39k39 w at M 39 a if 54 1 gr f Ag 2 5 119 f YE Chair 33 balmhr 7 1 Chair CV1 i 12 chair is higher in energy bc of 5 carbons in same area sterics chairmost stable a a my fe quotK l f H L V if if A and B SameCis C and D DifferentTrans Chapter 5 stereochemistry Stereoisomers same molecular form same connectivity cant convert between isomers via bond rotation C and D from above are Enantiomers 9 Handed Isomers Diastereomers are AB vs C AB vs D 9 not mirror images When reading stereochemistry Wedge UpOut Dash downback Axial up down Equatorial leftright Label with s and be CONSISTENT he pox V W rm a w Disub Cyclohexane AAxial EEquatorial 12cis aeea 12trans aaee 13cis aaee 13trans ae l4cis ae l4trans aaee Things don t like to be in axial because its costs energy Why do axial substituents cost energy Gauche Interactions Is it Chiral point of inversion plane of symmetry 0 Mirror plane 1 CisAchiral 2 TransChiral For A the methyl groups are identical on both sides so its achiral If atoms of interest have 2 or more of the same things attached to it then its ACHIRAL CIP Rules Find stereocenter 9 4 things attached Assign priorities for substituents 0 Based on atomic o l is highest and 4 is lowest If there is a tie go out until its broken Trace from 1 92 93 and orientate molecules so that lower priority points back Clock Wise R Counter Clock Wise S R Ibuprofen doesn t bind to anything but Slbuprofen kills pain by interrupting signalpathways S Naproxen kills pain while RNaproxen kills people kidneys
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