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chemistry
organic chemistry

Questions and Answers of Organic Chemistry

Solution A was prepared by dissolving potassium acetate in methanol. Solution B was prepared by adding potassium methoxide to acetic acid. Reaction of methyl iodide either with solution A or with
If the temperature is not kept below 25°C during the reaction of primary alcohols with ptoluenesulfonyl chloride in pyridine, it is sometimes observed that the isolated product is not the desired
The reaction of cyclopentyl bromide with sodium cyanide to give cyclopentyl cyanide
Write structural formulas for toluene (C6H5CH3) and for benzoic acid (C6H5CO2H) (a) as resonance hybrids of two Kekule forms and (b) with the Robinson symbol.
The heats of hydrogenation of cycloheptene and 1, 3, 5-cycloheptatriene are 110 kJ/mol (26.3 kcal/mol) and 305 kJ/mol (73.0 kcal/mol), respectively. In both cases cycloheptane is the product. What is
Write a structural formula for each of the following compounds: (a) o-Ethylanisole (c) p-Nitroaniline (b) m-Chlorostyrene
Chrysene is an aromatic hydrocarbon found in coal tar. The structure shown is not the most stable resonance form. Write the most stable resonance form for chrysene.
A single organic product was isolated after Birch reduction of p-xylene. Suggest a reasonable structure for this substance.
The reaction of N-bromosuccinimide with the following compounds has been reported in the chemical literature. Each compound yields a single product in 95% yield. Identify the product formed from each
Chromic acid oxidation of 4-tert-butyl-1, 2-dimethylbenzene yielded a single compound having the molecular formula C12H14O4. What was this compound?
Give the structure of the principal organic product formed on reaction of benzyl bromide with each of the following reagents: (a) Sodium ethoxide (d) Sodium hydrogen sulfide (b) Potassium
Both 1, 2-dihydronaphthalene and 1, 4-dihydronaphthalene may be selectively hydrogenated to 1, 2, 3, 4-tetrahydronaphthalene.
Each of the following reactions has been reported in the chemical literature and gives a single organic product in high yield. Write the structure of the product for each reaction. (a)
Both cyclooctatetraene and styrene have the molecular formula C8H8 and undergo combustion according to the equation C8H8 + 10O2 → 8CO2 + 4H2O The measured heats of combustion are 4393 and
One of the chemical properties that make cyclobutadiene difficult to isolate is that it reacts readily with itself to give a dimer:
Represent the electron distribution among the π orbitals in (a) [10]-Annulene (b) [12]-Annulene
What does a comparison of the heats of combustion of benzene (3265 kJ/mol; 781 kcal/mol), cyclooctatetraene (4543 kJ/mol; 1086 kcal/mol), [16]-annulene (9121 kJ/mol; 2182 kcal/mol), and [18]-annulene
Write resonance structures for tropylium cation sufficient to show the delocalization of the positive charge over all seven carbons.
Write resonance structures for cyclopentadienide anion sufficient to show the delocalization of the negative charge over all five carbons.
A standard method for the preparation of sodium cyclopentadienide (C5H5Na) is by reaction of cyclopentadiene with a solution of sodium amide in liquid ammonia. Write a balanced equation for this
Is either of the following ions aromatic?
Unlike quinoline and isoquinoline, which are of comparable stability, the compounds indole and isoindole are quite different from each other. Which one is more stable? Explain the reason for your
Can you deduce the structural formulas of benzoxazole and benzothiazole?
Imidazole is a much stronger base than pyrrole. Predict which nitrogen is protonated when imidazole reacts with an acid, and write a structural formula for the species formed.
Write structural formulas and give the IUPAC names for all the isomers of C6H5C4H9 that contain a monosubstituted benzene ring.
Write a structural formula corresponding to each of the following: (a) Allylbenzene (g) 2-Nitrobenzenecarboxylic acid (b) (E)-1-Phenyl-1-butene (h) p-Diisopropylbenzene (c)
Using numerical locants and the names in Table 11.1 as a guide, give an acceptable IUPAC name for each of the following compounds
Write structural formulas and give acceptable names for all the isomeric (a) Nitrotoluenes (d) Tetrafluorobenzenes (b) Dichlorobenzoic acids (e) Naphthalene carboxylic acids (c)
Mesitylene (1, 3, 5-trimethylbenzene) is the most stable of the trimethylbenzene isomers. Can you think of a reason why? Which isomer do you think is the least stable? Make a molecular model of each
Which one of the dichlorobenzene isomers does not have a dipole moment? Which one has the largest dipole moment? Compare your answers with the dipole moments calculated using the molecular-modeling
Identify the longest and the shortest carbon–carbon bonds in styrene. Make reasonable estimates of their bond distances and compare them to the distances in a molecular model.
The resonance form shown is not the most stable one for the compound indicated. Write the most stable resonance form.
Each of the following may be represented by at least one alternative resonance structure in which all the six-membered rings correspond to Kekule forms of benzene. Write such a resonance form for
Give the structure of the expected product from the reaction of isopropyl benzene with (a) Hydrogen (3 mol), Pt (b) Sodium and ethanol in liquid ammonia (c) Sodium dichromate, water, sulfuric
Each of the following reactions has been described in the chemical literature and gives a single organic product in good yield. Identify the product of each reaction.
A certain compound A, when treated with N-bromosuccinimide and benzoyl peroxide under photochemical conditions in refluxing carbon tetrachloride, gave 3, 4, 5-tribromobenzyl bromide in excellent
A compound was obtained from a natural product and had the molecular formula C14H20O3. It contained three methoxy (─OCH3) groups and a ─CH2CHoeC (CH3)2 substituent. Oxidation with either
Hydroboration–oxidation of (E)-2-( p-anisyl)-2-butene yielded an alcohol A, mp 60°C, in 72% yield. When the same reaction was performed on the Z alkene, an isomeric liquid alcohol B was obtained
Dehydrohalogenation of the diastereomeric forms of 1-chloro-1, 2-diphenylpropane is stereospecific. One diastereomer yields (E)-1, 2-diphenylpropene, and the other yields the Z isomer. Which
Suggest reagents suitable for carrying out each of the following conversions. In most cases more than one synthetic operation will be necessary
The relative rates of reaction of ethane, toluene, and ethylbenzene with bromine atoms have been measured. The most reactive hydrocarbon undergoes hydrogen atom abstraction a million times faster
Write the principal resonance structures of o-methylbenzyl cation and m-methylbenzyl cation. Which one has a tertiary carbocation as a contributing resonance form?
The same anion is formed by loss of the most acidic proton from 1-methyl-1, 3-cyclopentadiene as from 5-methyl-1, 3-cyclopentadiene. Explain.
There are two different tetramethyl derivatives of cyclooctatetraene that have methyl groups on four adjacent carbon atoms. They are both completely conjugated and are not stereoisomers. Write their
Evaluate each of the following processes applied to cyclooctatetraene, and decide whether the species formed is aromatic or not. (a) Addition of one more π electron, to give C8H8─ (b)
Evaluate each of the following processes applied to cyclononatetraene, and decide whether the species formed is aromatic or not: (a) Addition of one more π electron, to give C9H10─ (b)
From among the molecules and ions shown, all of which are based on cycloundecapentaene, identify those which satisfy the criteria for aromaticity as prescribed by Hackle’s rule.
(a) Figure 11.16 is an electrostatic potential map of calicene, so named because its shape resembles a chalice (calix is the Latin word for “cup”). Both the electrostatic potential map and its
Classify each of the following heterocyclic molecules as aromatic or not, according to Hackle’s rule:
Pellagra is a disease caused by a deficiency of niacin (C6H5NO2) in the diet. Niacin can be synthesized in the laboratory by the side-chain oxidation of 3- methylpyridine with chromic acid or
Nitroxoline is the generic name by which 5-nitro-8-hydroxyquinoline is sold as an antibacterial drug. Write its structural formula.
Acridine is a heterocyclic aromatic compound obtained from coal tar that is used in the synthesis of dyes. The molecular formula of Acridine is C13H9N, and its ring system is analogous to that of
Nitration of 1, 4-dimethylbenzene (p-xylene) gives a single product having the molecular formula C8H9NO2 in high yield. What is this product?
The compounds benzyl chloride (C6H5CH2Cl), (dichloromethyl) benzene (C6H5CHCl2), and (trichloroethylene benzene (C6H5CCl3) all undergo nitration more slowly than benzene, the proportion of
Write structural formulas for the cyclohexadienyl cations formed from aniline (C6H5NH2) during (a) Ortho bromination (four resonance structures) (b) Meta bromination (three resonance
Treatment of biphenyl (see Section 11.7 to remind yourself of its structure) with a mixture of nitric acid and sulfuric acid gave two principal products both having the molecular formula C12H9NO2.
Treatment of biphenyl (see Section 11.7 to remind yourself of its structure) with a mixture of nitric acid and sulfuric acid gave two principal products both having the molecular formula C12H9NO2.
Would you expect the substituent ─N (CH3)3 to more closely resemble ─N (CH3)2 or ─NO2 in its effect on rate and regioselectivity in electrophilic aromatic substitution? Why?
Reaction of chlorobenzene with 4-chlorobenzyl chloride and aluminum chloride gave a mixture of two products in good yield (76%). What were these two products?
Write the structure of the principal organic product obtained on nitration of each of the following: (a) p-Methyl benzoic acid (d) p-Methoxyacetophenone (b) m-Dichlorobenzene (e) p-Methyl
Write chemical equations showing how you could prepare m-bromonitrobenzene as the principal organic product, starting with benzene and using any necessary organic or inorganic reagents. How could you
Suggest an efficient synthesis of m-nitrobenzoic acid from toluene.
Suffocation of naphthalene is reversible at elevated temperature. A different isomer of naphthalenesulfonic acid is the major product at 160°C than is the case at 0°C. Which isomer is the product
On being heated with sulfur trioxide in sulfuric acid, 1, 2, 4, 5-tetramethylbenzene was converted to a product of molecular formula C10H14O3S in 94% yield. Suggest a reasonable structure for this
When benzene is prepared from coal tar, it is contaminated with thiophene, from which it cannot be separated by distillation because of very similar boiling points. Shaking a mixture of benzene and
Give reagents suitable for carrying out each of the following reactions, and write the major organic products. If an ortho, para mixture is expected, show both. If the Meta isomer is the expected
Write a structural formula for the most stable cyclohexadienyl cation intermediate formed in each of the following reactions. Is this intermediate more or less stable than the one formed by
In each of the following pairs of compounds choose which one will react faster with the indicated reagent, and write a chemical equation for the faster reaction: (a) Toluene or chlorobenzene with a
Arrange the following five compounds in order of decreasing rate of bromination: benzene, toluene, o-xylene, m-xylene, 1, 3, 5-trimethylbenzene (the relative rates are 2 x 107, 5 x 104, 5 x 102, 60,
Each of the following reactions has been carried out under conditions such that disubstitution or trisubstitution occurred. Identify the principal organic product in each case. (a) Nitration of
Write equations showing how you could prepare each of the following from benzene or toluene and any necessary organic or inorganic reagents. If an ortho, para mixture is formed in any step of your
Write equations showing how you could prepare each of the following from anisole and any necessary organic or inorganic reagents. If an ortho, para mixture is formed in any step of your synthesis,
How many products are capable of being formed from toluene in each of the following reactions? (a) Mononitration (HNO3, H2SO4, 40°C). (b) Dinitration (HNO3, H2SO4, 80°C). (c) Trinitration (HNO3,
Friedel–Crafts acylation of the individual isomers of xylene with acetyl chloride and aluminum chloride yields a single product, different for each xylene isomer, in high yield in each case. Write
In an attempt to prepare propylbenzene, a chemist alkylated benzene with 1-chloropropane and aluminum chloride. However, two isomeric hydrocarbons were obtained in a ratio of 2:1, the desired
Reaction of benzanilide (C6H5NHCC6H5) with chlorine in acetic acid yields a mixture of two monochloro derivatives formed by electrophilic aromatic substitution. Suggest reasonable structures for
Each of the following reactions has been reported in the chemical literature and gives a predominance of a single product in synthetically acceptable yield. Write the structure of the product. Only
What combination of acyl chloride or acid anhydride and arene would you choose to prepare each of the following compounds by a Friedel–Crafts acylation reaction?
Suggest a suitable series of reactions for carrying out each of the following synthetic transformations:
A standard synthetic sequence for building a six-membered cyclic ketone onto an existing aromatic ring is shown in outline as follows. Specify the reagents necessary for each step.
Each of the compounds indicated undergoes an intermolecular Friedel–Crafts acylation reaction to yield a cyclic ketone. Write the structure of the expected product in each case.
The partial rate factors for chlorination of biphenyl are as shown.
Partial rate factors may be used to estimate product distributions in disubstituted benzene derivatives. The reactivity of a particular position in o-bromotoluene, for example, is given by the
When 2-isopropyl-1,3,5-trimethylbenzene is heated with aluminum chloride (trace of HCl present) at 50°C, the major material present after 4 h is 1-isopropyl-2,4,5-trimethylbenzene. Suggest a
When a dilute solution of 6-phenylhexanoyl chloride in carbon disulfide was slowly added (over a period of 8 days!) to a suspension of aluminum chloride in the same solvent, it yielded a product A
Write a reasonable mechanism for the formation of cyclohexylbenzene from the reaction of benzene, cyclohexene, and sulfuric acid.
Reaction of hex methylbenzene with methyl chloride and aluminum chloride gave a salt A, which, on being treated with aqueous sodium bicarbonate solution, yielded compound B. Suggest a mechanism for
The synthesis of compound C was achieved by using compounds A and B as the sources of all carbon atoms. Suggest a synthetic sequence involving no more than three steps by which A and B may be
When styrene is refluxed with aqueous sulfuric acid, two “styrene dimers” are formed as the major products. One of these styrene dimers is 1, 3-diphenyl-1-butene; the other is 1-methyl-
Treatment of the alcohol whose structure is shown here with sulfuric acid gave as the major organic product a tricycles hydrocarbon of molecular formula C16H16. Suggest a reasonable structure for
Outline a synthesis of 1-phenylcyclohexene from benzene and cyclohexene.
The reaction shown gives a single product in 88% yield. What is that product?
In the simplest molecular orbital treatment of conjugated systems, it is assumed that the π system does not interact with the framework of σ bonds. When this MO method was used to calculate
Succinct anhydride, the structure of which is shown, is a cyclic anhydride often used in Friedel-Crafts acylations. Give the structure of the product obtained when benzene is acylated with succinct
Using benzene and any necessary organic or inorganic reagents, suggest efficient syntheses of (a) Isobutyl benzene, C6H5CH2CH (CH3)2 (b) Neopentylbenzene, C6H5CH2C (CH3)3
The partial rate factors for nitration of tert-butyl benzene are as shown.
Most of the NMR spectra in this text were recorded on a spectrometer having field strength of 4.7 T (200 MHz for 1H). The first generation of widely used NMR spectrometers was 60-MHz instruments.
What will be the 13C frequency setting of an NMR spectrometer that operates at 100 MHz for protons?
The 1H NMR signal for bromoform (CHBr3) appears at 2065 Hz when recorded on a 300-MHz NMR spectrometer. (a) What is the chemical shift of this proton? (b) Is the proton in CHBr3 more shielded or less
There is a difference of 4.6 ppm in the 1H chemical shifts of CHCl3 and CH3CCl3. What is the chemical shift for the protons in CH3CCl3? Explain your reasoning

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