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Organic Chemistry
Exam #3
| Question | Answer |
|---|---|
| The pi electrons of benzene are located: | Above and below the ring plane. |
| Anthracene | -It is a component of coal tar -(400-500 nm peak) |
| What reagents most effectively convert an aromatic compound into an unconjucated cyclohexadiene? | Na in NH3(l) |
| What is unusual about the electrophile normally used in sulfonation of aromatic compounds? | It is not a cation |
| Friedel-Crafts alkylation and acylation are similar but differ in one important way: | Only alkylation often involves rearrangements. |
| There is no such substituents as one that is both __ and ___-directing. | Activation; m- |
| Electrophilic | Reagent attracted to electrons that participates in chemical reaction by accepting an electron pair in order to bond to a nucleophile. electrophiles accept electrons, they are Lewis acids Most electrophiles are positively charged, have an atom that carri |
| Which substance should react most readily by nucleophilic aromatic substation? | 2,6-dinitrofluorobenzene |
| Nucleophilic aromatic substation | a substitution reaction in organic chemistry in which the nucleophile displaces a good leaving group, such as a halide, on an aromatic ring There are 6 nucleophilic substitution mechanisms encountered with aromatic systems |
| The highest energies are used in _____ spectroscopy of organic compounds. | UV |
| The H-NMR signal produced by the number 2 carbon from the left of CH3CHClOCH3 should have what shape? | a quartet |
| How many C-NMR signals is the compound para-dimethylbenzene (p-xylene) going to have? | 3 |
| Which special NMR technique allows you to associate specific H atoms with specific C atoms they are on? | HETCOR |
| Which IR band would be within the fingerprint region of a spectrum? (all answers are in WN (1/cm)) | 750 |
| The MS of CH3C(=O)CH2CH2CH3, the main organic product after workup will be: | 4-methyl-4-heptanol |
| Which organometallic reagents are dangerous neurotoxins? | Those of Hg |
| What organometallic reagents have Na+ as their metal allow adding alkyne groups to carbonyl compounds? | Acetylides |
| Grignard Reagents | -One major requirement in their synthesis reaction: solvents must be ethers. - |
| Carbenes | is a molecule containing a neutral carbon atom with a valence of two and two unshared valence electrons. The general formula is R-(C:)-R' or R=C:. |
| H-NMR | -Also known as Proton NMR. -Large singlet with no splitting usually means isolated methyl. -Classic isopropyl signal group: a septet (area 1) and a big doublet (area 6). |
| C-NMR | -The alkyl carbons should be identified as 45 = methine, 30 = methylene and 22 = methyl (probably) - |
| UV | -If you have UV absorbance then you have an aromatic compound or a non aromatic compound with 2 or more conjugated double bonds. |
| MS | -Fragment at 43 is a great match for COCH3 from a methyl ketone. - |
| SODAR | (2C+2+N-H-X)/2 C= Carbons; N= Nitrogens; X= Halogens -Shows how many pi bonds and/or rings you have in your compound. -IF the number is greater than 4 it usually indicated an aromatic compound. |
| IR | -Bands at 3300 indicated OH groups -Large bands at 1716 indicated C=O - |
| The MO structure of benzene has ___ bonding ____ anti bonding, and ____ nonbonding pi orbitals with 6pi electrons. | 3,3,0 |
| Aromatic compound aniline has the _____ group as a substituent on the basic benzene structure. | -NH2 |
| When styrene (vinylbenzene) is treated with HCl, what is the major product formed? | 1-chloro-1-phenylethane |
| Electrophilic Aromatic Substitution (EAS) | -First step involving the ring is electrons from the ring pi system attack the reagent. -Most require a cation or cationic reagent |
| Sulfonation | Neutral species in EAS. |
| Meta position | 1,3 position |
| Para Position | 1,4 position |
| Ortho Position | 1,2 position |
| Which of the following groups, when on a benzene ring, will both activate the ring and meta direct new EAS? | None of these: -NO2, -Br, -OH |
| If ou wish to reduce the product of a Friedel-Crafts acylation to a hydroaron, which reagent(s) will work? | Zn(Hg)+HCl |
| Starting with toluene, using any needed reagents, which 3 steps best make 3-Bromo-5-nitrobenzoic acid? | H2SO4/NaCr2O7/HEAT; HNO3/H2SO4; BR2/FeBr3 |
| H-NMR Cont... | -Classic splitting pattern of an isolated ethyl group is a triplet (area 3) and a quartet (area 2) - |
| An unknown organic sub stand has a C-NMR spectrum with 5 peaks, at 14, 22, 24, 44, and 203 ppm. It is NOT: | CH3CH2CH2CH2OH |
| IN PERFORMING AN IR SPECTROSCOPIC ANALYSIS, WHAT SUBSTANCE MUST BE AVOIDED WITh NORMAL IR METHODS? | Water |
| To correlate the H-NMR and C-NMR spectra of a compound, so that you know which C have which H, you use: | HETCOR |
| HETCOR, COSY, FTIR, DEPT | DEPT= tells you how many H are on each C atom in a C-NMR |
| The majority of simple organometallic compounds are ____ and react vigorously with _____. | Nucleophiles ; water |
| If a ketone is treated with excess Grignard or Lithium reagent, the main organic product formed by workup is: | Tertiary Alcohol |
| An example of an activation group which is also ortho, para directing would be: | -CH3 |
| The normal reagent sequence used to place an n-butyl group on a benzene ring would be: | CH3CH2CH2COCl+ AlCl3, then HCL +Zn(Hg) |
| If you treat 1-bromo-2-nitrobenzene with Cl2 +AlCl3, where will the Cl most likely be placed? | C-4 and C-6 |
| Which analytical method does NOT rely on the presence of energy levels of some type within a molecule? | MS |
| The two common forms of 'hyphenated MS' combinee MS with: | Chromatography |
| The most common alkenylbenzene compound, used in making a variety of polymers, is: | Styrene |
| In order to be useful for substitution reactions of aromatic reigns, a reagent must be classified as a (an) | Electrophile |
| Sulfonation of benzene is unusual in two ways; which two? | The active reagent is not an ion and it is very reversible |
| The hydrogens on the second carbon atom of 1-chlorobutane should have a H-NMR signal which is: | a triplet of triplets |
| Which is a limitation of 13C-NMR as it is usually perfumed? | peak area doesn't correspond to the number of C |
| In infrared Spectroscopy the peaks that are largest are produced by: | Highly polar bonds |
| Which of the following should have a significant UV spectrum (produce absorbances in the UV range)? | 2-Phenylpropane |
| Organometallic reagents like Grignard and Lithium reagents are usually made by reacting: | Alkyl Halides and Metals |
| When a Grignard reagent is reacted with formaldehyde (H2C=O) and then worked up normally, the product is: | a primary alcohol |
| If we react excess CH3CH2MgBr wit hthe ester CH3CH2COOCH3, the major product formed after workup is | (CH3CH2)3COH |
| The Simmons-Smith Reagent | -CH2I2 + Zn(Cu) -Used to transform alkenes into cyclopropyls |
| When organometallic chemists study the bonding and stability of complexes, they see if the electron count on the metal is ___ , which indicates greater stability. | 18 |
| Which is correct as a description of the MO model of pi orbitals in benzene or other arenas? | the pi MO's are above and below the ring |
| In naming the benzene ring as a substituent (C6H5-) the name it is usually given is | phenyl |
| the usual products formed by Birch Reduction of aromatic rings with Na in NH3(l) would be called: | 1,4-cyclohexadienes |
| Annulenes with ____ pi electrons satisfy Hückel's rule; therefore they _____ "aromatic" | 10; are (4n+2), n=2 |
| Sulfonation of an aromatic ring is most often performed using a reagent of | SO3 + H2SO4 |
| In general, if a substituent always adds electron density to an aromatic ring, that substituent will be: | an activating, ortho, para-director |
| which species, if it is already on an aromatic ring, will tend to prevent Friedel-Crafts alkylation of the ring? | -NO2 |
| What sequence of reactions would be convert toluene into 2-bromo-4-nitrobenzioc acid? | HNO3 + H2SO4, then Br2, then heat with acidic aq dichromate. |
| Pyridine is significantly less reactive than benzene in electrophilic aromatic substations reactions because | the N in the ring reacts with Bronsted or lewis acids |
| In the H-NMR spectrum of 1-propanol, CH3CH2CH2OH, which of the hydrogens' signals will be further upfield: | That of CH3 |
| What shape will the H-NMR signal from the methyl group in 1-propanol be? | Triplet |
| Relatively stable in contact with water? | (CH3)4Si |
| Grignard reagents can be used to make alcohols; tertiary alcohols form by Grignard reaction with | Ketones |
| Several reagents can be used to make cyclopropyl rings from alkenes, including all the following: | CH2I2 + Zn(Cu), CHCl3+K(+)(-OC(CH3)3), and CH2N2 |
| Metallocenes are transition metal organometallic compounds which use ___ ligands. | cyclopentadienide |
| The Heck and Suzuki reaction are both useful organometallic syntheses using ___ as a key part of the process | Pd |
| Electrophilic cont... | Most electrophiles are positively charged, have an atom that carries a partial positive charge, or have an atom that does not have an octet of electrons |
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