Concept explainers
Interpretation:
A step by step mechanism for both the transformation of Robinson annulation sequence is to be provided, and the acidity of
Concept introduction:
Electrophiles are electron deficient species that have positive or partially positive charge. Lewis acids are electrophiles that accept electron pair.
Nucleophiles are electron rich species that have negative or partially negative charge. Lewis bases are nucleophiles that donate electron pair.
Free radical is an atom, molecule, or ion that has an unpaired electron that makes it highly chemically reactive.
Substitution reaction: A reaction in which one of the hydrogen atoms of a hydrocarbon or a functional group is substituted by any other functional group is called substitution reaction.
Elimination reaction: A reaction in which two substituent groups are detached and a double bond is formed is called elimination reaction.
Addition reaction: It is the reaction in which unsaturated bonds are converted to saturated molecules by the addition of molecules.
A base removes acidic hydrogen and forms an enolate.
The enolate adds to the
A carbon–carbon bond formation occurs by aldol addition and aldol condensation reaction.
An aldol reaction takes place in a protic solvent with a base.
An aldol reaction takes place by acid catalysis, and direct dehydration of
A
A chemical reaction that is catalyzed by a base is called base catalyzed reaction.
Aldol reaction is preferred in basic condition over acidic condition, as after the aldol condensation, acid catalysis promotes the reaction further.
In Robinson annulation reaction, Michael addition, followed by simple aldol condensation, takes place.
The Robinson annulation reaction is used to form one ring on to another.
A resonance structure which stabilize the conjugate base also increases the acidity.
The rules for drawing resonance structures are as:
Only nonbonding electron pairs and pi electrons can participate in conjugation in the formation of various resonating structures.
The single bonds present in the molecule do not break or form in the resonance structures.
The placement of atoms present in the molecule remains fixed.
The octet of all atoms is completely filled.
More the number of resonance structures indicate higher stability of a compound.
Want to see the full answer?
Check out a sample textbook solutionChapter 19 Solutions
Organic Chemistry
- When phenyl 3,4-dimethylbenzoate undergoes electrophilic aromatic substitution, one ring reacts much more readily than the other. (a) Which one is it? Encircle the ring (b) Explain your answer. (c) Draw the resulting product/s when it undergoes bromination reaction. Product (c) (a) Explanation (b)arrow_forwardCompound A undergoes an acid-catalyzed hydrolysis. One of the products (B) that is isolated gives the following 1H NMR spectrum. Identify the compounds A and Carrow_forwardGive the structure of the product formed on reaction of ethyl acetoacetate with each of the following: (a) 1-Bromopentane and sodium ethoxide (b) Saponification (basic hydrolysis) and decarboxylation of the product in part (a) (c) Methyl iodide and the product in part (a) treated with sodium ethoxide (d) Saponification and decarboxylation of the product in part (c) (e) 1-Bromo-3-chloropropane and one equivalent of sodium ethoxide (f) Product in part (e) treated with a second equivalent of sodium ethoxide (g) Saponification and decarboxylation of the product in part (f) (h) Phenyl vinyl ketone and sodium ethoxide (i) Saponification and decarboxylation of the product in part (h)arrow_forward
- (i) The enolisation of ketone A can generate an equilibrium mixture of A and either enol B or enolate C. Give the structure of both B and C, and the mechanism for their formation from A under the given conditions. (ii) A HCI (cat.) NaOH (cat.) B с Draw the structure of the product obtained when A is dissolved in D3O*. Give a detailed mechanism to account for the structure you propose.arrow_forwardPredict the major products of the following reactions, including stereochemistry where appropriate. (a) potassium tert-butoxide + methyl iodide (b) sodium methoxide + tert-butyl iodidearrow_forwardConsider the tetracyclic aromatic compound drawn below, with rings labeled as A, B, C, and D. (a) Which of the four rings is most reactive in electrophilic aromatic substitution? (b) Which of the four rings is least reactive in electrophilic aromatic substitution? (c) What are the major product(s) formed when this compound is treated with one equivalent of Br2?arrow_forward
- B-Damascenone belongs to a family of fragrant natural products called rose ketones that have been used in the perfume industry. In one synthesis of B-damascenone, the reaction of compound 1 with one equivalent of MCPBA afforded two constitutionally isomeric epoxides (compounds 2 and 3), which were then converted into diol 4 upon subsequent treatment with aqueous acid. Identify the structures of epoxides 2 and 3, and propose a mechanism that converts each of them into compound 4 in the presence of H30+. OCH, OH OCH, МСВРА 2 +3 (one equiv.) OH B-Damascenonearrow_forwardPropose a synthesis for each of the following compounds. (a) OH (b) (c)arrow_forwardExplain how benzaldehyde and dimedone reacts with each other, and then with the aminotriazole to form compound 1a in the presence of an acid catalyst. Provide a detailed reaction mechanism and explanation.arrow_forward
- 4) Aromatic compounds are among the most abundant and versatile in nature. From a synthetic point of view, these compounds, despite their stabilities, are quite useful and can undergo reactions under special conditions and by specific mechanisms, such as the Electrophilic Aromatic Substitution (SAE) and the Nucleophilic Aromatic Substitution (SNAr). Based on this, please answer the following items: (b) How would you prepare the following compounds starting from benzene? Explain the second in a different wayarrow_forward(c) Treating lactone B with two equivalents of phenylmagnesium bromide, followed by hydrolysis in aqueous acid, gives a compound with the molecular formula C18H22O2, as shown below. Propose a structural formula for this compound. 1. PhMgBr (2 eq.) 2. H'/H>O C18H2202 bj 1o 14 10I f6 40 & 3 4 00 (8)arrow_forwardIdentify products A and B from the given 1H NMR data. Treatment of CH2=CHCOCH3 with one equivalent of HCl forms compound A. A exhibits the following absorptions in its 1H NMR spectrum: 2.2 (singlet, 3H), 3.05 (triplet, 2 H), and 3.6 (triplet, 2 H) ppm. What is the structure of A?arrow_forward
- Organic ChemistryChemistryISBN:9781305580350Author:William H. Brown, Brent L. Iverson, Eric Anslyn, Christopher S. FootePublisher:Cengage Learning