content

media type="custom" key="15222" =Alkynes=

nomenclature
media type="custom" key="8187098"
 * 1) the basics - be able to draw a molecule from the name
 * 2) [| Reusch] (alkenes and alkynes)

elimination of dihalides

 * 1) first E-2 easy, second hard (use strong base like sodamide/ high temp)
 * 2) use geminal or vicinal dihalides
 * 3) [|Reusch]

addition and SN2 reactions of alkyne salts

 * see below under Reactions of alkynes

Reactions of alkynes

 * 1) [|Reusch]
 * 2) NaNH2 (made from Na/NH3 with Fe3+) with terminal alkynes to give salt
 * 3) Ag+ or Cu+ to precipitates of MCC-R
 * 4) alkyne salt SN2 reaction with primary alkyl halides and E-2 with secondary and tertiary alkyl halides
 * 5) alkyne salt addition to ketones and aldehydes to give alcohols
 * 6) reduction with H2/Pt or Pd catalysts to alkane
 * 7) reduction with H2/Lindlar's catalyst to cis alkene
 * 8) reduction with Na/NH3 to trans alkene
 * 9) addition of halogens to trans alkenyl dihalides then vicinal tetrahalides
 * 10) Markovnikov addition of HBr or HCl to alkenyl halides then geminal dihalides
 * 11) Markovnikov addition of H2O using Hg++/H2O/H2SO4 to methyl ketones via tautomerism of an enol
 * 12) Anti-Markovnikov addition of H20 using 1)BH(sia)2 (disiamylborane) 2)H2O2,OH- to aldehydes via tautomerism of an enol
 * 13) Anti-Markovnikov addition of HBr using HBr/a peroxide to an alkenyl halide then a geminal dihalide
 * 14) Cold dilute permanganate to diketones
 * 15) Hot concentrated permanganate to cleave alkyne bond then oxidize to carboxylic acids (or CO2 for terminal alkynes)
 * 16) Ozonolysis to cleave alkyne bond to carboxylic acids
 * 17) migration of triple bond to terminal alkyne using hot NaNH2
 * 18) migration of triple bond to more stable internal alkyne (if there is one) using hot KOH

Practice Problems

 * [|Reusch1]
 * [|Reusch2]
 * [|UCalgary]
 * [|Towson1]
 * [|Towson2]

Problem alkyne-2


=Alcohols=

Nomenclature

 * the basics - be able to draw a molecule from the name
 * [|Reusch]

Preparation

 * 1) hydrolysis of alkyl halides with hydroxide
 * 2) Markovnikov addition of water on alkenes using acid/water (watch for rearrangment of carbocation)
 * 3) Markovnikov addition of water on alkenes using 1) Hg(OAc)2 2) NaBH4 (oxymercuration - demercuration)
 * 4) Anti-Marknovnikov addition of water on alkenes using 1) BH3 2) NaOH, H2O2 (hydroboration - oxidation)
 * 5) hydroxylation of alkenes to syn glycols using cold dilute permanganate or OsO4, or anti glycols using peracids with aqueous acids [|Reusch 5i>]
 * 6) Reduction of aldehydes and ketones with NaBH4 or LiAlH4
 * 7) Reduction of esters or carboxylic acids with LiAlH4 (NaBH4 does not react)
 * 8) Reduction of aldehydes and ketones with Raney Ni (also reduces alkenes)
 * 9) synthesis of tertiary alcohols from Grignard or organolithium reagents with esters, acid chlorides or ketones [|UCalgary]
 * 10) synthesis of secondary alcohols from Grignard or organolithium reagents with aldehydes
 * 11) synthesis of primary alcohols from Grignard or organolithium reagents with formaldehyde or ethylene oxide
 * 12) remember that Grignard or organolithium reagents react with even weak acids (terminal alkynes, alcohols, thiols, carboxylic acids, etc.) to replace the metal with H
 * 13) thiols (R-SH) prepared by adding excess NaSH to alkyl halides or tosylates

Reactions

 * 1) dehydration to alkenes using a strong acid (e.g. H2SO4) via E-1, watch out for 1,2 shifts (can use reduction of alkene with Pd/H2 as a 2 step route from alcohols to alkanes)
 * 2) oxidation of primary alcohols to aldehydes via PCC (secondary alcohols go to ketones also but cheaper reagents can be used)
 * 3) oxidation of primary alcohols to carboxylic acids and secondary alcohols to ketones via general pupose oxidizers (e.g. CrO3, KMnO4, NaCr2O7)
 * 4) ROH to RCl using SOCl2 for primary and secondary alcohols (SOCl2 without base gives retention of chirality via SNi mechanism) [|Wikipedia]
 * 5) ROH to RCl using PCl3 for primary and secondary alcohols (inversion of chirality SN2)
 * 6) ROH to RBr using PBr3 for primary and secondary alcohols (inversion of chirality SN2)
 * 7) ROH to RBr using HBr for tertiary alcohols (SN1)
 * 8) ROH to RI using P/I2 for primary or secondary alcohols
 * 9) ROH to RBr using HBr for secondary and tertiary alcohols (via SN1)
 * 10) ROH to RCl using HCl/ZnCl2 fastest for tertiary alcohols and slow with secondary alcohols (SN1) Lucas test
 * 11) ROH to esters using acid chlorides (better) or mixing alcohol and carboxylic acid with acid catalyst and removing water
 * 12) ROH and H3PO4 (phosphoric acid) heat to make some phosphate esters (e.g. trimethyl phosphate) - most alcohols will undergo E-1 and dehydrate to alkenes, as described above
 * 13) ROH and HNO3 (nitric acid) to make nitrate esters (explosive, e.g. nitroglycerin)
 * 14) ROH to ROTs (tosylates) using TsCl, useful for doing SN2 reactions from primary alcohols:
 * 15) ROTs to RH using LiAlH4 (another way to go from alcohol to alkane in 2 steps)
 * 16) ROTs to RNH2 using ammonia
 * 17) ROTs to ROH using hydroxide
 * 18) ROTs to RX using halide salt (F-,Cl-,Br-,I-)
 * 19) ROTs to RCN (nitrile or cyanide) using NaCN
 * 20) with NaH, Na (primary or secondary alcohols) or K (for tertiary alcohols) to generate alkoxides
 * 21) phenols are much more acidic than aliphatic alcohols (phenolates can be made with hydroxide, electronegative groups make more acidic) [|Reusch]
 * 22) Williamson ether synthesis (alcoxide with primary alkyl halides or tosylates, secondary or tertiary give E-2)
 * 23) tertiary glycols undergo pinacol rearrangement
 * 24) glycols are converted to aldehydes or ketones using periodic acid (HIO4), thus hydroxylation then HIO4 is an alternative to straight ozonolysis of alkenes
 * 25) Thiolates are more nucleophilic and less basic than alcoxides so can do SN2 with primary or secondary alkyl halides and tosylates (tertiary give E-2) [|Reusch]
 * 26) thiols oxidized by KMnO4, HNO3 to sulfonic acids (R-SO3H)
 * 27) thiols oxidized by Br2 to disulfides (R-SS-R), also used by proteins

Practice Problems

 * [|Reusch1] [|Reusch2] [|Reusch3] (nomenclature)
 * [|Reusch4] [|Reusch5] [|Reusch6] [|Reusch7] (reactions)
 * [|Towson1] [|Towson2]

TEST 1
=Infrared Spectroscopy (IR)= =Mass Spectrometry (MS)= =Nuclear Magnetic Resonance Spectroscopy (NMR)=
 * [|Reusch]
 * measures the bending and stretching of bonds
 * higher wavenumber (in cm^-1) corresponds to higher energy
 * heavier atom gives lower energy and lower wavenumbers
 * higher bond energies (e.g. single -> double -> triple bonds) give higher wavenumbers
 * useful range 1600-3500 cm^-1 (any absorptions below that are in the fingerprint region)
 * C=C unconjugated alkene 1640-1680
 * C=C conjugated alkene 1620-1640
 * C=C aromatic 1600
 * C-H (sp3) 2900-3000
 * C-H (sp2) 3000-3100
 * C-H (sp) 3300
 * hydrogen bonded N-H, O-H broad near 3300, CO2H very broad 2500-3500
 * C=O ketone, aldehydes, carboxylic acids 1710
 * C=O conjugated ketone or aldehyde 1680
 * C=O esters 1730-1740
 * C=O amides 1640-1680
 * C=O acid chlorides 1780
 * C=O cyclobutanones 1780
 * C-H aldehyde 2700 and 2800
 * C=N 1660
 * CN (nitrile) 2250
 * CC alkyne 2150
 * [|Reusch]
 * molecules acquire a charge then are separated by mass in the mass spectrometer by moving in a magnetic field
 * M+ is molecular ion peak
 * base peak is the strongest peak
 * high resolution MS can give elemental analysis because atoms have non integer masses
 * C-13 is about 1%, thus there will be a small M+1 peak
 * for methyl M-15, ethyl M-29, propyl M-43, butyl M-57
 * for Br M+2 = M+
 * for Cl M+2 = 1/3 M+
 * for N, M+ is odd
 * for S M+2 = 4% M+
 * alcohols that can dehydrade often M+ not seen, only M-18
 * break C-C bonds to form stable carbocations (tertiary, benzylic, allylic)
 * [|Reusch]
 * can view every H and C in molecules as peaks
 * scale in ppm (delta scale), relative to tetramethylsilane (TMS), defined as zero
 * in a typical NMR plot, higher ppm are on the left (low field, more deshielded)
 * integration corresponds to number of Hs
 * electronegative elements deshield
 * adjacent and non-equivalent (2-3 bonds) H's couple with each other and split peaks (N+1 rule), giving coupling constant J
 * J for alkenes: cis 10 Hz, trans 15 Hz, geminal 2 Hz
 * J for aromatics: ortho 8 Hz, meta 2 Hz
 * CH2 next to chiral center are diastereotopic and the H's are not equivalent
 * alkanes 0.9-1.5 ppm
 * aromatics 7-8 ppm
 * alkenes 5-6 ppm
 * aldehydes 9-10 ppm
 * terminal alkyne H 2.5 ppm
 * benzylic or next to ketone or aldehyde 2.1 - 2.3 ppm
 * CH2-X (X = O,N,halogen) 3 - 4 ppm
 * carboxylic acid 10-12 ppm, although may be very broad
 * amine and alcohols may be broad, very variable and not undergo 3 bond coupling
 * in ultrapure samples, H of OH may exhibit 3 bond coupling and splitting
 * hydrogen bonding H's can be replaced with H NMR invisible D's by adding D2O or CD3OD
 * C NMR do not show C-C coupling because only about 1% of C's are C-13
 * C NMR are usually proton spin decoupled so that only singlets are obtained
 * C NMR shifts: carbonyl 160-210 ppm, aromatic 100-150 ppm, alkynes 75-95 ppm, alkanes 0-35 ppm

Problems

 * [|Reusch All NMR (scroll down)]
 * [|UCalgary All Spectroscopy]

=Ethers=
 * [|UCalgary]
 * R-O-R
 * nomenclature - be able to draw molecule from name - note special names for epoxides
 * somewhat polar but bp close to alkanes
 * can solvate cations and form complex with Grignard reagents
 * hydrogen bond acceptor but not a donor
 * cyclic ethers: epoxides (oxiranes), oxetanes, furans, THF (tetrahydrofuran) is common solvent

synthesis

 * Williamson ether synthesis
 * Alkoxymercuration-demercuration of alkenes using 1) Hg(OAc)2, ROH 2) NaBH4 (Markovnikov addition of an alcohol)
 * Dehydration of alcohols using strong acid (e.g. H2SO4) poor method because competing E-1
 * epoxides from alkenes and peracid (e.g. MCPBA)
 * epoxides from cyclization of halohydrin (H2O, Cl2, NaOH)

reactions
=Sulfides=
 * with HI and HBr to cleave and give 2 alkyl halides (aromatic ethers stop at phenol stage)
 * with oxygen to give explosive hydroperoxides
 * epoxides open in base with nucleophile attacking sterically less hindered side (e.g. alkoxide, Grignard)
 * epoxides open in acid with nucleophile attacking sterically more hindered side (e.g. alcohol)
 * nomenclature: thiols, thioethers, sulfides
 * RSH more acidic than alcohols (similar to phenols)

Reactions

 * thiolates react with primary or secondary alkyl halides (or tosylates) to give thioethers (with tertiary would give E-2)
 * thioethers react with H2O2 to give sulfoxides then sulfones

Synthesis
=Ultraviolet Spectroscopy= =Reactions of Conjugated Systems= =Aromatic compounds= media type="custom" key="14908"
 * thiols can be made with alkyl halides (or tosylates) with excess NaSH
 * the more extended the conjugation the longer the wavelength (lower the energy) of absorption
 * in UV spectra, +30 nm for extending conjugation and +5 for alkyl
 * molecular orbitals of allylic and butadiene systems
 * 1,2 and 1,4 addition of HBr or NBS to conjugated dienes
 * SN2 reactions of allylic halides
 * Diels-Alder reaction: diene must be s-cis, endo rule, stereospecificity (avoid 1,3 relationship of D and W)
 * cycloadditions [2 + 2] thermally disallowed but photochemically allowed
 * cycloadditions [4 + 2] thermally allowed but photochemically disallowed
 * aromaticity adds stability beyond just conjugation
 * required for aromaticity: a complete ring of co-planar p orbitals and 4N + 2 pi electrons
 * required for anti-aromaticity: a complete ring of co-planar p orbitals and 4N pi electrons
 * forming an aromatic structure upon losing a proton leads to high acidity alkanes (e.g. cyclopentadiene)
 * predict weak and strong bases depending on changes in aromaticity
 * nomenclature: ortho, meta, para, phenyl, benzyl