Chemistry 228 Chapter Notes

 

IR and NMR Spectroscopy (from chapters 2 and 9)

 

Homework: From chapter two: 2.29,  31 and 47;   from chapter four: 4.50, and 51; and from chapter nine:  9.29, 30, 31, 32, 33, 35, and 36.

Electromagnetic Radiation Basics

•  Refresh your memory on basic theory - see general chemistry test and/or physics text.

•  Relationships among E, h, c, l, n.  Equations will be given; know how to use them.

 

IR spectroscopy

•  Understand the theory of IR spectroscopy.

•  How is IR electromagnetic radiation absorbed by organic molecules ?

•  How are dipole moment changes and the observations that the CΊC stretch of ethyne, the C=C stretch of ethene, and the symmetric stretch of methane are not observed in the IR ?

•  Be able to use a table relating frequency range of absorption to identify functional groups.

•  Mono and di substituted benzenes give a characteristic IR pattern in the 680 to 860 cm-1 region. Be able to predict the substitution pattern of substituted benzenes given this data.

•  How is l related to n ?

 

NMR spectroscopy

•  Understand the theory of NMR spectroscopy.

•  What is nuclear spin ?

•  How is NMR electromagnetic radiation absorbed by organic molecules ?

• What is TMS and how is d (chemical shift) defined ?

•  How do Fourier transform (FT) instruments differ from sweep (CW) instruments ?

•  Be able to draw a block diagram of a  CW NMR spectrometer.

•  Why are FT NMR spectrometers filled with liquid helium and nitrogen ?

•  How is chemical shift related to electronegativity and hybridization of groups attached ?

•  Be able to use a 1H NMR which contains splitting patterns and integrations along with a table relating chemical shift range to determine the structure of an organic molecule.

•  Be able to predict 1H NMR and  13C NMR (BB only) spectra for organic molecules

•  What is  a DEPT Spectrum ?

Mass spectroscopy 

•  What is it? How does it work?

 

 

Tying it all together.

•  Be able to use data from IR and NMR to determine the structure of an organic molecule.

Chapter 11 Notes

 

Homework:11.25, 26, 27, 28, 29, 30, 32, 33, 34, 37, and 47.

•  Nomenclature of simple alcohols and ethers

•  Physical properties of alcohols and ethers.

•  Hydrogen bonding - what is it ?

•  Synthesis of alcohols

      -  acid-catalyzed hydration

            -  limitations of this method

            -  regiochemistry: Markovnikov. Why ?

            -  stereochemistry:  racemic. Why ?

      -  oxymercuration-demercuration

            -  regiochemistry: Markovnikov. Why ?

            -  stereochemistry:  racemic. Why ?

            -  Be able to demonstrate why alkyl or hydride migration in the carbocation is rare.

      -  hydroboration-oxidation and hydroboration-protonolysis

            -  regiochemistry: antiMarkovnikov. Why ?

            -  stereochemistry:

                    -  syn addition of B-H followed by retention in replacement (by OH or H) of B.

            - Why doesn’t alkyl or hydride migration cause carbon skeletal rearrangement.

•  Mesylates and Tosylates

      -  How are alcohols converted into mesylates and tosylates ?

      -  Why are these groups such good leaving groups ?

•  Conversion of alcohols into alkylhalides by HX, PBr3 or SOCl2

      -  Know the SN1 mechanism for conversion of a 3° or 2° alcohol, ROH, into RX by HX.

•  Synthesis of ethers (know the mechanisms)

      - dehydration of alcohols

      - Williamson synthesis

•  Reactions of ethers

      -  What is oxonium ?

      -  Cleavage by strong acids at high temperatures.

• Epoxides (oxiranes)

      -  synthesis from alkenes, syn addition

      -  acid catalyzed ring opening (know the mechanism)

            -  regiochemistry:attack at the more substituted carbon (most stable carbocation)

            -  stereochemistry: anti

      - base catalyzed ring opening (know the mechanism)

            -  regiochemistry: attack at the less substituted carbon (sterically less hindered)

            -  stereochemistry: anti

 

                       

• Figures 11.5 (page 531  should be helpful.

 

Chapter 12 Notes

 

Homework:12.11, 12, 13, 14, 16, 21, and 29.

•  Be able to recognize oxidations and reductions involving O and H as well as halogens.

•  Be able to label a carbonyl compound as an aldehyde, ketone, carboxylic acid or an ester.

•  Polarity of carbonyl group.

•  Hydride reducing agents: LiAlH4, NaBH4.

       -Which carbonyl compounds will each reduce ?

      - What are the products ?

      -  Outline of mechanism:  H:– attacks carbonyl, followed by H+ addition to alkoxide.

•  Oxidation

      - Be able to recognize Cr6+ oxidizing agents

            -  Aqueous and methylene chloride soluble (PCC) reagents

            -  Why does the PCC reagent stop oxidizing at the aldehyde stage ?

            -   Basis for “test for 1° and 2° alcohols”.  How?

•  KMnO4 oxidations

•  Organometallic reagents:  Organolithium and Grignard reagents

      -  Preparation

      -  Polarity

      -  Reactivity with epoxides and aldehydes and ketones.

 Chapter 13 Notes

 

Homework:13.17, 18, 21(ignore mass spec), 23, 24, 26, 28(read text then try it), 29(read text then try it), and 35

Conjugated systems

•  How do p orbitals and sp2 hybridization relate to conjugation.

 

Electromagnetic Radiation Basics

•  Refresh your memory on basic theory - see general chemistry test and/or physics test.

•  Relationships among E, h, c, l, n.  Equations will be given; know how to use them..

 

UV/Vis spectroscopy

•  Understand the theory of UV/Vis spectroscopy.

•  Be able to draw a block diagram of a UV/Vis spectrophotometer.

•  How is UV/Vis electromagnetic radiation absorbed by organic molecules ?

      -  HOMO, LUMO, p->p*, n->p*

      -  How is conjugation related to l max  and HOMO, LUMO, p->p*, n->p*?

      -  What is e ?

•  Be able to use A = e C l  equation for a quantitative calculation.

•  How is the visible spectrum is related to colors we perceive ?  Be able to used the data below to discuss visible light absorption and color perception.

 

 

 

complementary

l (nm)

color

color

< 400

UV

 

425

violet

yellow

470

blue

orange

520

green

red

570

yellow

violet

620

orange

blue

680

red

green

>700

IR

 

 

 

Reactions of conjugated systems

•  Be able to draw resonance structures and resonance hybrids of cations.

•  Know mechanisms for the 1,2 and 1,4 and 1,6  . . .  reactions.

•  Diels-Alder reaction

      - products

      - What is the stereochemistry of the adduct when cis or trans dienophiles are used.

      - effect of electron withdrawing/donating groups on diene/dienophile.

Chapter 14 Notes

 

Homework: (12.27 yes chapter 12); and 14.16, 18, 19, 20, 25, 29, 30, and 31; and learning group problem #2.

•  Nomenclature of benzene derivatives.

      - know how to use ortho, meta and para for disubstituted benzenes

      - when to use phenyl

      - know the following names: xylene, toluene, phenol, aniline, benzenesulfonic acid, benzoic acid, acetophenone, anisole.  Also know the nitro group.

•  Stability of benzene

•  Aromatic compounds in general.

      - molecular orbital explanation of stability.

      - resonance explanation of stability.

      - requirements for aromaticity: cyclic, planar, 4n + 2 delocalizable e-.

      - annulenes

      - benzoid/nonbenzoid polycyclic

      - heterocyclic

 

Chapter 15 Notes

 Homework:15.26, 27, 29, 31, 34, 35, 41, 44

•  General mechanism (i.e., E+ as electrophile) for electrophilic aromatic substitution.

•  Reaction coordinate for electrophilic aromatic substitution (as in figure 15.3 (page 665)). What is the difference between an intermediate and a transition state?

•  Specific mechanisms for electrophilic aromatic substitutions: halogenation, nitration, sulfonation, alkylation, acylation.  Know how the electrophile is generated and how, in the final step,  the H+ is removed (what is the base?) .

•  How do the Lewis acids catalyze the Friedel-Crafts reactions?

 

•  Effect of substituents on reactivity and orientation on electrophile addition.

      - Learn table 15.2 (page 680).

      - activation  . . . . . . . . deactivation

      - ortho/para directors and meta directors.

 

•  Be able to use resonance structures of the arenium cation intermediate to to explain how

      -  electron withdrawing groups deactivate the rings by the inductive effect.

      -   electron withdrawing groups are meta directors by the inductive effect.

 

      -   electron releasing groups activate the rings by the inductive effect.

      -   electron releasing groups are ortho/para directors by the inductive effect.

 

      -   groups that have lone pairs activate the rings by the resonance effect.

      -   groups that have lone pairs are ortho/para directors by the resonance effect.

 

•  Halogen substituents are a bit mysterious.  Halogens deactivate the ring by the inductive effect while they are ortho/para directors by the resonance effect.  In organic chemistry nothing is black and white; shades of gray dominate.

 

•  When there are two substituents on a ring where does an incoming electrophile go ?

 Chapter 16 Notes

 

Homework:16.23-28, 43 and 44.

•  IUPAC nomenclature of aldehydes and ketones. Also know common names:

      - acetone, formaldehyde, acetaldehyde, acetophenone and benzophenone.

•  Trends in mp, bp and solubility in water.

•  keto-enol tautomerization

•  Synthesis of aldehydes

-  ozonolysis of alkenes

-  oxidation of 1° alcohols (Why use PCC ?)

-  reduction of acyl chloride, esters and nitriles

•  Synthesis of ketones

-  ozonolysis of alkenes

-  Friedel Crafts acylation

-  oxidation of 2° alcohols (aqueous chromic acid is okay)

-  addition of water to alkynes

-  lithium dialkylcuprates and acyl chlorides

- nitriles

•  Nucleophilic addition reactions of aldehydes and ketones.

-  polarity of carbonyl

-  be familiar with strong nucleophile mechanism and the acid-catalyzed mechanism.

-  reactivity: aldehydes versus ketones.

      -  the effect of electron withdrawing/donating groups.

-  hydrates, hemiacetal, acetals and thioacetals (Raney Ni reduction).

      - Why is chloralhydrate so stable ? What is a protecting group ?

•  Ammonia addition

-  derivatives: oxime, hydrazines (e.g. 2,4-DNP), semicarbazide

-  Wolff-Kisner reduction.

•  Hydrogen Cyanide (HCN) addition.

•  Wittig reaction

•  Reformatsky reaction

•  Baeyer-Villiger reaction.  What is migratory aptitude ?

Chapter 17 Notes

Homework:17.31, 32, 34, 35, and 37.

•  acidity of a and b hydrogens on aldehydes and ketones.

•  resonance structures and resonance hybrid of the enolate anion

•  know the keto-enol tautomerization especially through the enolate intermediate.

•  reactions via enols and enolates

            -  racemization: acid catalyzed and base catalyzed.

            -  halogenation: acid catalyzed and base promoted.

 

• haloform reaction

• aldol reactions

            -  identify nucleophile and electrophile

            -  crossed reactions

            -  practical implementation of a crossed reaction

            -  Claisen-Schmidt

            - cyclization

            - acid catalyzed aldol reactions

•  Addition to a,b unsaturated aldehydes and ketones

            -  strong nucleophiles (simple addition)

            -  weak nucleophiles (conjugate addition)

            -  organocopper reagents

            -  Michael addition

 

 Chapter 18 Notes

 

Homework:

•  Nomenclature of carboxylic acids

      - Systematic names like methanoic acid  . . .  decanoic acid, and benzoic acid

      -  Know theses common names: formic, acetic, propionic, and butyric.

      -  Know the names of these dicarboxylic acids:  oxalic, malonic,  and succinic.

•  Water solubility of carboxylic acids: C1 to C4 soluble, C5 to C18 decreasingly soluble.

•  How do resonance effect and inductive effect explain acidity of carboxylic acids.

•  Be able to predict pKa trends in a series of carboxylic acids.

•  Be able to recognize derivatives of carboxylic acids: esters, anhydrides, acyl chlorides, amides,  and nitriles.

•  Nomenclature of carboxylic acid derivatives: esters, anhydrides, acyl chlorides, amides, and nitriles.

•  Spectroscopy (IR, 1H NMR, 13C NMR) of carboxylic acids and derivatives.  You will be given necessary tables of IR frequencies and NMR chemical shifts .

•  Preparation of carboxylic acids

      - oxidation of alkenes

      - oxidation of aldehydes and primary alcohols

      - side chain (1°, 2°) of alkyl benzenes

      - oxidation of methyl ketones (haloform reaction)

      - hydrolysis of cyanohydrins or nitriles

      - carbonation of grignard reagents

•  Nucleophilic substitution of acyl compounds (nucleophilic addition-elimination)

      - general mechanism

      - Why is this substitution rare in aldehydes and ketones (which are acyl compounds)?

      - relative reactivity of acyl compounds: acyl chloride > acid anhydride > ester > amide

•  Acyl chlorides

      - synthesis from carboxylic acids and SOCl2, PCl3, or PCl5

      - nucleophilic substitution of acyl chlorides by carboxylates, alcohols, and amines.

•  Acid anhydrides

      - synthesis

      - nucleophilic substitution of acid anhydrides by alcohols and amines

•  Esters

      - synthesis from carboxylic acid and alcohol (acid catalyzed esterification)

            - where does –O– come from ? (the alcohol; as demonstrated by an 18O isotope label)

            -  how does acid catalyzed hydrolysis compete with acid catalyzed esterification ?

            -  lactones: cyclic esters from intramolecular acid catalyzed esterification of g or d hydroxy acids

                  -   why almost exclusively g or d hydroxy acids ?

                  -   why then is Erythromycin A, a m latone, stable ?

      - synthesis from acyl chloride and alcohol

            - where does –O– come from ? (the alcohol; as demonstrated by an 18O isotope label)

      - synthesis from acid anhydrides and alcohol

            - where does –O– come from ? (the alcohol; as demonstrated by an 18O isotope label)

       - base promoted hydrolysis of esters (saponification)

            - KNOW THE MECHANISM

            - how did an 18O isotope label experiment help elucidate the mechanism ?

            - how did studies with chiral esters help elucidate the mechanism ?

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            - how does soap (detergents in general) clean ?

            - what is a surfactant ?

•  Amides

      -  synthesis form acyl chlorides, anhydrides, and esters.

      -  hydrolysis of amides

            - acidic

            - basic

      -  Nitriles

            -  synthesis by nucleophilic substitution of alkyl halides by cyanide.

            -  hydrolysis of nitriles

            -  lactams: cyclic amides

                        - why are g or d lactams stable ?

                        - why are b lactams reactive ?

                                    - how does penicillins work ?