fall 2017 organic chemistry i review by elizabeth … · 8:32am-8:41am ch7 alkyl halides and...

Disclaimer: The definitions & photos used herein belong to: Organic Chemistry by David Klein 2nd edition, Wiley publishers

Fall 2017 Organic Chemistry I Review by Elizabeth Ruelke for SARC 12/2/17 8:00-8:02am Intro/disclaimer

8:02-8:04am Ch1 structure and bonding o Mass number weight of the atom o Atomic weight o S orbital located within sigma bonds o P orbital located within pi bonds o Valence electrons located on the outer shell o Bonding electrons shared between atoms o Nonbonding electrons located locally on one atom o Lewis structures structure showing the electron location on atoms o Formal charge charge on the overall molecule cumulated from the individual charges on each atom. o Isomers same molecular formula, different arrangement of atoms. o Octet rule there must be 8 electron in the outer shell o Resonance electrons movement throughout molecule

Delocalized lone pairs participate in resonance Localized lone pairs don’t participate in resonance

o VESPR theory electron repulsion yields different molecule geometry hybridizations. Sp3 no lone pairs is tetrahedral; one lone pair is pyramidal; two lone pairs is bent Sp2trigonal planar Splinear

o Condensed formula written out molecular formuala without written bonds CH3CH2CH3 o Electronegativity increases up and to the right of the periodic table

8:04-8:06am Ch2 acids and bases o Lewis acid electron acceptor

Bronsted acid proton donor (aka LA) o Lewis base electron donor

Bronsted base proton acceptor (aka LB) o Keq= [products]/[reactants] o pKa= -log Ka o Increasing acidity goes down and to the right on periodic table o Comparing acidity of certain molecules: MARIO

Molecule make sure you’re comparing similar molecules Atom make sure you evaluate the electronegativity of the atoms Resonance the more resonance available the better the acid Induction the more inductive effects the more acidic Orbital the more s character in orbital the more acidic


8:07am-8:09am Ch3 organic molecules and functional groups

o Intermolecular forces van der waals dipole-dipole hydrogen bonding ionic

o Boiling point increases with more hydrogen bonding Larger the surface area higher the BP

o Melting point more globular/symmetrical higher MP o SolubilityLike dissolves like

8:09am-8:16am Ch4 alkanes o Straight chain vs branched chain o Cycloalkanes o Nomenclature w/substituents

Always prioritize lowest number to substituents, giving preference to alcohols o Newman projections (staggered, eclipsed) (anti/gauche) o Angle strain any angle below/above 109.5°C

Cyclopropane o Torsional strain energy from overlapping groups (eclipsed)

Cyclobutane o Steric strain energy from overlapping electron clouds

t-butyl group base o Chair/Boat conformation (ax/eq) & ring flipping


o Constitutional isomers same molecular formula, different connections o Stereoisomers (cis/trans) same molecular formula, same connections, different special arrangement o OIL RIG (oxidation/reduction)

Oxidation is loss of electrons, or increased oxygen connections Reduction is gain of electrons, or decreased oxygen connections

o Problems: Nomenclature: m-chlorophenol Newman projection: C2-C3 3-chloro-2-butanol

Lowest energy conformer Highest energy conformer

Chair/Boat: cis 1,3-diethylcyclohexane vs. trans 1,3-diethylcyclohexane Lowest energy? Highest energy?

Stereoisomers or constitutional isomers or same? (CH3)3CCH2CH(CH3)2 and (CH3)2CHCH2C(CH3)3

8:16-8:22am Ch5 stereochemistry o Achiral vs Chiral

R clockwise (dextrorotary: polarized light to the right) S counterclockwise (levorotary: polarized light to the left) Meso optically inactive

o Stereoisomers: Enantiomers mirror images, non-superimposable Diastereomers not superimposable and not mirror images

o Two enantiomers have identical physical properties except polarimetry o Optically active has chirality, not meso, part of chemical property of a substance o Racemic definition 50/50 mixture of enantiomers

o Specific rotation [a]= specific rotation a=observed rotation c=concentration (g/mL) l= path length (dm)

o Enantiomeric excess o Problems:

Draw both R/S of 2-chloro-2butanol Draw both R/S of 3-bromo-3-chlorohexane Specific rotation:

You add 0.3g of sucrose to 10mL water. Run the sample across 10cm length. The observed rotation is +1.99°. What is the specific rotation?

Enantiomeric excess: Scientist was to create synthetic adrenaline, but experiment is contaminated. Pure adrenaline is -

53. The observed rotation is -45. What is the ee%? ***Note: final number is the excess don’t forget to add the difference of racemic***

8:22-8:32am Ch6 understanding Organic reactions o Substitution rxn replacing X with Y on a molecule o Addition rxn adding molecules across double or triple bonds o Elimination rxn removing HX from molecule to create double bond o Bond making /bond forming

Concerted mech single step Stepwise mech two step, with intermediate state

o Bond cleavage: Heterolytic one of the pair of atoms receives both electrons

Carbocations: C+ Carbanions: C:--

Homolytic electrons are evenly split between atoms Radicals: C•


o Electrophile atom lacking electron density, vulnerable to attack o Nucleophile atom/bond with lone pair electrons, will attack substrate o ∆H= bonds broken – bonds formed

Endothermic + ∆H absorbs heat from system Exothermic - ∆H releases heat into system

o Thermodynamics ∆G= ∆H – T∆S Exergonic releases energy into system Endergonic absorbs energy from system Keq >1 correlates with ∆G (-) favors products Keq <1 correlates ∆G (+) favors reactants

o Energy diagrams Peaks=transition state Valley=intermediate

o Energy of activation (Ea) difference in energy between reactants and transition state Catalysts speeds up reaction rate, usually acids or metals; lower activation energy

o Kinetics= study of reaction rate o Rate= k [reactants]

Sn1 rate= k[reactant] Sn2 rate= k[reactant][nucleophile]

o Problems Substitution, Elimination, or Addition?

Chlorobutane + HBr Bromobutane + HCl 2,4-dibromobutane + 2NaH 2-butyne + 2HBr Butane + Br2 1,2-dibromobutane Acetylene + 2HBr 1,2-dibromoethane 2-bromopropane + NaOH 2-propanol + HBr 2,2-dichloropentane + NaNH2 2-chloro-2-pentene + NH3

Identify electrophilic and/or nucleophilic sites on the following: Phenol Pentanol 3-bromo-2-hexanol Carboxylic acid

Draw the following energy diagrams: Exergonic 2 step rxn Endergonic 2 step rxn Exergonic 1 step rxn Endergonic 1 step rxn

8:32am-8:41am Ch7 alkyl halides and nucleophilic substitution o Vinyl halide & Aryl halides unfavored and unreactive in substitutions

o Allylic halide & Benzylic halide favored and reactive in substitutions

o Nomenclature

Common names: t-butyl-, isobutyl-, sec-butyl-, isopropyl- o Bond polarity based off relative electronegativity’s of the atoms on bond o Good leaving groups easily leave the molecule, usually halides o Nucleophilicity increases to the right and down periodic table

Steric hindrance can determine site of attack See NaOH versus t-butoxide


Substitution Reactions Sn1 Sn2 Rate =k[reactant] =k[reactant][nucleophile] Mechanism Stepwise (carbocation intermediate) Concerted Substrate Res > 3° > 2° > 1° 1° > 2° > 3° Nucleophile Weak Strong Solvent Protic: water, acetic acid, ammonia Aprotic: DMSO, DMF, acetonitrile Product Type Racemic mixture Inverted chirality due to back-side attack

o Hammond postulate (Sn1) shows 3° has lower activation energy over 2° for carbocation formation o Problems

Show product, arrow pushing and indicate Sn1 or Sn2: 2-bromo-3-methylpentane + H2O 2-bromo-3-methylpentane + NaOH 2-pentanol + TsOH/py 2-methyl-3-OTs-pentane + EtOH 2-chlorobutane + NaCN 3-bromo-3-methylpentane + H2O 1-chloro-3-methylpentane + NaOH 2-methylcyclohexanol + H2O 2-iodocyclopentane + MeSH

8:41-8:50am Ch8 alkyl halides and elimination reactions

Elimination Reactions E1 E2 Rate =k[reactant] =k[reactant][nucleophile] Mechanism Stepwise (carbocation intermediate) Concerted Substrate 3° > 2° > 1° 3° > 2° > 1° (antiperiplanar) Base n/a Strong

o Hammond postulate (E2) shows trans substitution is preferred over cis o Trans Alkene more stable than cis alkene due to steric strain o E/Z nomenclature:

E largest groups on opposite sides of double bond Z largest groups on same side of double bond

o Zaitsev rule: indicates the most stable alkene is the more substituted double bond Zaitsev more substituted product Hoffman lesser substituted product *** Triethylamine & t-BuOK give preferential Hoffman product

o Nucleophile vs Base

o o Problems

List E1, E2, Sn1, or Sn2 for below and major/minor products Chloropentane + NaBr 3-bromo-3methyl-pentane + NaSH 2-bromopentane + NaH Bromopentane + NaOH 2-bromopentane + NaOH 2-bromo-3-methylpentane + H2O

8:50-9:00am BREAK TIME


9:00-9:06am Ch9 Alcohols, Ethers, and related compounds o Nomenclature

Naming alcohols

Naming epoxides

Naming Ethers o Synthesis

Williamson ether synthesis Epoxide have angle strain

Breaking in acid addition at more substituted side Breaking in base addition at less substituted side

Alcohol Addition of primary alcohol (1. BH3, THF 2. H2O2, OH) Addition of secondary alcohol (H2SO4) Elimination of alcohol via E1 of 2°/3° degree alcohol Elimination of alcohol via E2 of 1° degree alcohol

o LeChatelier’s principle o Reagents

NaH strong base, preparation of ethers TsCl, py replace OH to be good leaving group H2SO4dehydration if concentrated, hydration if dilute HCl acid breaking of epoxide KOH base breaking of epoxide NaNH2 base NaOCH3 formation of ether with base POCl3 in py replace alcohol with chloride (backside attack) SOCl2 replace alcohol with chloride (backside attack) PBr3 replace alcohol with bromine (backside attack) NaCN base, and elongation of carbon chain Br2/I2 adds trans vicinal halides KSH replace alcohol or break epoxide ring; adds thiol group (backside attack) Disulfide Zn/Hcl thiol groups

o Problems: Give product(s) Acetylene 1. NaH, 2. MeBr 3. H2, Lindlars 4. Dilute H2SO4 2-butanol 1. H2SO4, heat, 2. HBr 3. t-BuOK 1,2-epoxycyclohexane 1. NaBr 2. NaH 3. Br2 1-pentene 1.BH3, THF 2. H2O2, OH 3. TsOH, py 4. NaSH 1,2-epoxy-2-methylcyclohexane 1. NaOH 2. POCl2, py

9:06-9:12am Ch10 alkenes o Calculating the degrees of unsaturation ½(2C +2 + N – H – X)

Each degree represents 2 less H, or an additional double bond o Nomenclature (vs alcohol, functional groups, etc)

-diene, -triene, E/Z (cis/trans)


o Making alkenes -OCH3 vs –OC(CH3)3 different products acid (H2SO4 on alcohol) vs base (-OCH3)

o Reagents Hydrohalogenation (HX) Hydration (H2O, H2SO4) Halogenation (X2) Halohydrin formation (X2, H2O) Hydroboration-oxidation (1. BH3, THF, 2. H2O2, -OH)

o Markovnikov addition hydrogen goes with more hydrogens o Problems: Show arrow pushing

2-butanol + H2SO4, heat 2-butanol + -OCH3 Pentene + HBr 2-butene + H2O, H2SO4 2-butene + Br2 2-pentene + Br2/H2O Pentene 1. BH3, THF 2. H2O2, OH

9:12-9:18am Ch11 alkynes o Nomenclature (-diynes, -triynes)

If alkene and alkyne, go with the lower numbering o Preparation of alkynes from alkenes

NaNH2, NaH, etc o Reactions to alkynes

H2, lindlar’s (cis addition) H2, pt (reduce to alkane)

NaNH3 (trans addition to alkyne) X2 Water addition Acid tautomerization (enol to keto)

H2O, H2SO4, HgSO4 (more substituted alcohol) BH3, THF 2. H2O2, -OH (lesser substituted alcohol)

Elongating carbon chains Add epoxides (then H2O) to give terminal OH

o Retroynthesis (final beginning product): go back one step/precursor at a time o Synthesis (acetylene) given final o Problems

Acetylene 1. NaH 2. EtBr 3. NaH 4. MeBr 5. H2, lindlar’s Acetylene 1. NaH 2. PropylBr 3. Br2 (excess) Acetylene 1. NaH 2. Oxirane 3. H2O Acetylene 1. NaH 2. EtBr 3. BH3, THF 4. H2O2, OH Acetylene 1.NaH 2. MeBr 3.NaH 4. MeBr 5. H2SO4, HgSO4, H2O

9:18-9:25am Ch12 Oxidation reduction o Reducing agents

Na NH3 (trans) NaBH4 LiAlH4 (LAH)

o Oxidation agents KMnO4/OsO4 syn addition) MCPBA (expoy) RCO3H 2. H2O (anti diol addition) O3 2. Zn, H2O (cleavage of alkene)

Carboxylic acids on alkynes) K2Cr2O7 (or CrO3 with H2SO4, H2O) (yield ketone) PCC (ketone)

o Problems Butanal 1. LAH excess 2. H2O 3.TsOH, py 4. NaBr 5. NaH 2-pentanol 1. CrO3, H2O, H2SO4 2. NaBr 3. H2O Acetylene 1.NaH 2. MeBr 3. Br2 4. KMnO4, cold


Propanol 1. H2SO4, heat 2. Br2 3. NaH (2eq) 4. NaNH3 5. MCPBA Cyclopentene 1. O3 2. Zn, H2O 3. LAH (excess) 4. H2O 2-methylcyclopentanol 1. TsOH, py 2. NaBr 3. NaH 4. RCO3H 5. H2O

9:25-9:32am Ch13 Mass Spec & IR spectroscopy o Mass Spec

Yields molecular formula, presence of Br/Cl, via fragmentation and detection of carbocations Base peak (100%), mass-to-charge (m/z), (M)+• most common fragment, (M+1)+• second most abundant

fragment (M+2)+• chlorine (1:3 ratio peaks), bromine (1:1 ratio peaks)

Fragmentation/Loss: M-15 (methyl), M-29 (ethyl), M-43 (propyl), M-57 (butyl), M-18 (H2O) Problems

Molecular formula?

Bromine, Chlorine, or neither?

o IR spec

Yields functional groups present on molecule, via bending and stretching Diagnostic region: 4000-1500 (cm-1) most important frequencies Fingerprint region: 1500-400 (cm-1) don’t pay attention to this Shifting is affect by % s character, bond length, difference in weight between atoms Signals can be broad, strong, or weak


Problems

Carboxylic acid, alcohol, neither?


Carboxylic acid, alcohol, amine, neither?

Match


9:32-9:40am Ch14 NMR o H NMR

Comparing signals: homotropic, enantiotropic, diastereotropic Characteristics:

Location (aka shift δ) determined by inductive neighbors o Downfield (high number) vs upfield (low number)

o

o

o


Area (integration I) how many protons are represented in the signal o Height represents integration relative to each other (ratio) 2:3:2:3

o Shape (splitting m) how many neighbors (n+1)

o o Singlet= no neighbors; doublet= 1 neighbor; triplet= 2 neighbors, etc.

o Problems

Determine number of signals

Determine number of signals and shift

o C NMR

Identify number of signals of C13

Range:


Types of C NMR:

Problems

Determine number of signals, shift, integration

Determine structure

9:40-9:45am Ch15 Radical Reactions

o Radical stability: res > 3° > 2° > 1° > Me


o Definitions

o o Stages:

o Initiator (heat, light, NBS, Acyl peroxides) Propogation Termination

o Types chlorination (more energy favorable, incomplete product formation) vs bromination (complete product formation, higher energy state)

o Product racemic o Reagent HBr, ROOR (gives anti-markovnikov product) o Problems

Acetylene 1.NaH 2.MeBr 3.NaH 4.MeBr 5.HBr, ROOR 2-butene 1.Br2 2. NaH (2eq) 3. NaNH3 4. NBS, hv

9:45-10:00am Final survey, Questions, and Closing Statements o Please leave room clean

fall 2017 organic chemistry i review by elizabeth … · 8:32am-8:41am ch7 alkyl halides and...

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