Final Exam ACS Study Guide Fall21 Organic Chemistry 2021 PDF

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CHEM 301 Lecture Final Exam: Selected Study Guide

Fall 2021

FINAL EXAM Summary Sheet Potential Study Questions Disclaimer: The following are potential topics for exam questions and sample questions; the exam may or may not contain these questions, and questions not included in this sheet may or may not be on the exam. There also may be typos in this sheet. ALKANES Physical Properties - Hydrocarbons, dispersion forces, non-polar, not miscible w/water, low density - sp3 hybridized carbon: C-C, C-H bonds, electronegativity, MO theory & orbitals - m.p.: odd/even effect - b.p. C1-4: gases; C5-17: liquids, C18 and up: solids - linear, branched, cyclics, chirality (incl. optical activity, D/L, R/S, d/l,+/-), - non-equivalent carbons - isomers: constitutional, conformational isomers, stereo-isomers - naming; special groups: o Me, Et, Pr, Bu o iPr, iBu, sec-Bu, tBu o neopentyl Task: Name compounds 1 and 2; identify any chiral centers and # of chemically non-equivalent carbons; where would the compounds absorb in IR in UVvis? Identify the participating orbitals.

1

-

2

Rotational/conformational isomers = conformations o eclipsed  values: H/H; CH3/H; CH3/CH3 o staggered, anti, gauche  value: gauche: CH3/CH3

Task: draw an energy rotational energy plot (360°) for pentane along C2-C3 bond - Cycloalkanes: o Spiro, fused, bridged: naming o Heats of combustion: ring strains (angle, torsional, sterics) o Cis/trans o 1,3-diaxial interactions  value H/CH3 o Ring-flip for cyclohexane

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CHEM 301 Lecture Final Exam: Selected Study Guide

Fall 2021

Task: draw compound 3 as chair; determine cis and/or trans in 4, name compound 5; determine any chiral centers.

4

5

3

Chemical Rxns - Fairly unreactive - Combustible: rxn w/oxygen => CO2 and H2O + heat - Bond Dissociation Energies: how to work them out to calculate ΔH Task: combustion of butane: formulate the rxn - (Photo)halogenation: Cl2 and Br2 with hv or Δ o Radical mechanism  Initiation  Propagation  Termination o Selectivity: Cl2 vs Br2 o Energy vs Rxn progress diagram  Thermodynamics: ΔG, ΔH, transition state, Hammond postulate  Kinetics: rate, order, activation energy, catalysis Task: formulate the rxn of 1,1-dimethylcyclobutane with Cl2/hv; propose the relative ratio of the products formed. Task: draw an exothermic rxn diagram: label ΔH, transition state, activation energy

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CHEM 301 Lecture Final Exam: Selected Study Guide

Fall 2021

ALKYLHALIDES Physical Properties - Slight dipole moment depending on geometry; higher bp than corresponding hydrocarbons; electronegativities; relative bond lengths/bond strengths o VSEPR: geometries - Non-polar, not misc. w/water; higher density; good solvents; freons - Naming: o Some common names: CH2Cl2, CHCl3, CCl4, … Chemical Reactions A. Synthesis a. Photohalogenation o With Br2 or Cl2 o Allyl and benzyl compounds with NBS => allyl and benzyl bromide b. Nucelophilic Substitution: R-L + Hal- => R-Hal + L○ R-L + Hal- => R-Hal + L○ R-OH + HBr ○ R-OH + PBr3 ○ R-OH => sulfonates, sulfates, phosphates: make excellent leaving groups ○ Other good leaving groups: rank excellent, good/moderate, poor ○ compare/contrast: SN1 vs. SN2 i. solvents ii. reagents iii. nucleophiles iv. leaving groups v. mechanism: carbocations & rearrangements (SN1); SN2 vi. kinetics c. Addition Rxns to alkenes: - halogenation => vicinal dihalide - hydrohalogenation => alkylhalide d. Addition Rxns to alkynes - halogenation => vicinal tetrahalide - hydrohalogenation => geminal dihalides B. Reactions a. Grignard (Chapter 10) b. SN1 + SN2 c. E1 + E2 d. Carbenes: CHBr3, CHCl3; CH2I2 (for Simmons Smith) Task: Formulate and example for all reactions mentioned under Synthesis and Reactions

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CHEM 301 Lecture Final Exam: Selected Study Guide

Fall 2021

ALKENES Physical Properties - Hydrocarbons, dispersion forces, non-polar, not miscible w/water, low density - sp2 hybridized carbon: MO theory & orbitals, geometry - m.p., b.p very similar to alkanes: C1-4: gases; C5-17: liquids, C18 and up: solids - FT-IR - isomers: stereo-isomers: cis/trans; E/Z - naming; special groups: o methylene, vinyl, allyl, benzyl, phenyl o ethylene, styrene, isoprene, isobutylene, …. - Stability & heats of hydrogenation Chemical Reactions A. Synthesis for Alkenes - Elimination Rxns o Alcohols + acid H3O+ (acid = conc. H2SO4, H3PO4, …) o Alkylhalides + base: E1 (weak base = solvent; carbocation), E2 (strong base; antiperiplanar) o Vicinal dibromide + NaI - Hydrogenation of Alkynes (Lindlar and Na/NH3) - Catalytic Cracking B. Reactions of Alkenes - Addition Rxns: see hand-out - Metathesis - Polymers - Think about the stereochemical implications of the reactions: if the alkene is cis ( or trans) how will the stereochemistry of the former two C=C carbons be affected by the mechanism? Will the reaction outcome/product(s) be optically active? The answer is typically: no; because, either a racemate is formed (the two products are chiral, but since they are formed in 50:50 ratio, the product is a racemate); or, the compound formed is a meso compound (not chiral and not optically active).

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CHEM 301 Lecture Final Exam: Selected Study Guide

Fall 2021

ALKYNES Physical Properties - Hydrocarbons, dispersion forces, non-polar, not miscible w/water, low density - sp hybridized carbon: MO theory & orbitals, geometry - m.p., b.p very similar to alkanes: C1-4: gases; C5-17: liquids, C18 and up: solids - FT-IR - Degree of unsaturation - Acidity: compare with alkenes, alkanes and other compounds - naming; special groups: o acetylene, acetylide Chemical Reactions A. Synthetic routes towards Alkynes - Elimination Rxns o Alkyldihalides + base: E2  KOH: internal triple bond  NaNH2: terminal triple bond - From carbides B. Reactions of Alkynes - Nucleophilic substitutions o Terminal alkyne + strong base => acetylide = strong nucleophile and base o Can do SN2 (primary alkylhalides) and E2 reactions o Reacts with carbonyl compounds => alcohols - Addition Rxns o Br2 and Cl2 => tetrahalides o HBr, HCl => germinal dihalides (Mark.) o HBr/peroxides => geminal dibromide (Anti-Mark.) - Hydration o HgSO4/H2SO4/H2O (Mark.): ketones o Sia2BH/H2O2/OH- (Anti-Mark.): aldehydes and ketones o Keto-Enol Tautomerism - Oxidation o KMnO4/ cold water => vicinal ketones o KMnO4/warm/ OH- => acids (and CO2 for terminal triple bond) o Ozone/H2O => acids and formic acid (for terminal triple bond) -

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CHEM 301 Lecture Final Exam: Selected Study Guide

Fall 2021

ALCOHOLS (Chapters 10 & 11) Physical Properties - Polar protic –OH group: H-bonding (value =21 kJ/mol per H-bond); high b.p. - ‘acidic’ H on OH group; pKa of aliphatic alcohols vs. phenols • alcohols with electronegative groups: how do they modulate pKa? • phenols • thiophenols • alkanethiols • alkynes - Naming: common names and IUPAC; special phenols, diols, triols, what is phenol, hydroquinone? - physical properties of alcohols: - miscibility of alcohols - hydrogen bonding (value = …..kJ/mol) - comparison of boiling points with other classes of compounds Classes of sulfur compounds: - thiols - sulfides - disulfides - sulfone - sulfoxide - sulfonic acid Chemical Reactions A. Synthetic routes towards Alcohols - 1° Alkylhalides + OH- Alkenes Rxns o Hydration:  H 3O +  Oxymercuration  Hydroboration  Cl2 or Br2 and H2O o Diols  KMnO4  OsO4  Peroxyacid / Epoxides - Reactions with Carbonyl compounds o Acetylenes as Nucleophiles o Grignards and lithium organmetallic R-Li compounds as Nucleophiles  Aryl, vinyl, allyl, alkyl, and cycloalkyl halides (I, Br, Cl) work © 2021 MRKorn Liberty University

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CHEM 301 Lecture Final Exam: Selected Study Guide

Fall 2021

 solvents must be ether(s) for Grignards, ether or hexanes for LiR  cannot tolerate any protic groups/compounds/solvents  cannot tolerate functional groups similar to C=O  existing carbonyl groups will also react o With reducing agents: NaBH4, LiAlH4, H2/Raney-Ni  Selectivity • NaBH4 • LAH • H2/Raney-Ni B. Reactions of Alcohols (chapter 11) Oxidation Reactions • 1° ROH to aldehydes • 2° ROH to ketones • 3° ROH no rxn - Strong oxidizers o Chromic acid based; HNO3; excess of bleach/TEMPO - Mild oxidizers o PCC, Dess Martin Periodinane (DMP), Swern o NAD+ / NADH Reduction Reactions - to Alkanes o via alkene, then hydrogenation o via tosylate, then LAH - to Alkylhalides (I, Br, Cl) o HCl, HCl/ZnCl2, HBr o PBr3, PCl3, PCl5, P/I2 o SOCl2 o Some reagents are more effective than others o Mechanism: HCl, HBr: SN1; PBr3 etc. , SOCl2 = SN2 - to Alkenes o H2SO4, H3PO4, sulfonic acids o Via E1, higher temperatures - to symmetrical Ethers o H2SO4, H3PO4, sulfonic acids o Via SN1, lower temperatures

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CHEM 301 Lecture Final Exam: Selected Study Guide

Fall 2021

Unique Reactions of Glycols Pinacol Rearrangement o Glycol to ketone via rearrangements Cleavage of cis glycols o Alkene  cis-diol  aldehydes and ketones (can start from alkene, but does not need to start there) o HIO4 is the reagent to react with the glycol o Same products as if ozonolysis of the starting alkene Esters - General chemistry: alcohol-OH + H-Acid => ester + HOH (for H-Acid = carboxylic acid: Fischer esterification; H+ catalyzed; equilibrium) - More general: alcohol + acid derivative (anhydride, acid chloride, acid)  ester + small byproduct Esters based on carboxylic acids - Our typical esters: e.g. ethyl acetate: CH3COOCH2CH3; the carbonyl side came from the acid (its OH part was removed), the OR side from the alcohol (its H atom was removed). Esters based on inorganic acids For inorganic acids, draw the Lewis structure and find the HO part: this will be removed and will combine with the H from the alcohol ROH. - Sulfate esters: based on sulfuric acid H2SO4; e.g. CH3OSO3H - Nitrate esters: based on nitric acid: HNO3; e.g. TNT - Phosphate esters: based on phosphoric acid: H3PO4; e.g. DNA Ethers - Generating alkoxides: ROHROo Na, K, NaH, KOH (excess), NaOH (excess) - Reactions of Alkoxides o Can be aliphatic or aromatic o Alkoxides are strong nucleophiles (SN2) and strong bases (E2)  Williamson Ether Synthesis: alkoxide + alkylhalide  (mixed) ether (via SN2)  the alkoxide will be the more substituted one, the alkylhalide the less substituted

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CHEM 301 Lecture Final Exam: Selected Study Guide

Fall 2021

OTHER TOPICS Solvents - polar protic compounds: acids (pKa = 5-ish), alcohols (pKa = 16-ish), water (pKa = 15.7); - polar aprotic compounds: acetone, DMF, DMSO, … Acids/Bases - pKa from the table - H2S, phenols, thiols - Equilibrium rxns - Strong bases: LDA, NH2- hydrocarbons Functional Groups Task: name all functional groups O

O

N H

O

O Br

O

OH

OH OH

HO O O

N

N

Stereochemistry Task: Identify all stereocenters; draw the Fischer projection into a line structure O

O Br OH

Br H Br

CHO H OH H CH3

Equilibria etc. Give an example for - tautomers - stereoisomers - ring flip - dissociation of a weak acid - resonance

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