Sulfur and Selenium Chemistry Overview

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Questions and Answers

What type of addition occurs during the hydroboration of alkenes?

Radical addition

Electrophilic addition

Anti addition

Syn addition (correct)

In the reduction of alkynes using hydroboration, what is the end product when NaOH and H2O2 are used?

Aldehyde (correct)

Alkene

Ketone

Alcohol

What type of compound is produced when borane is transformed in the presence of NaOH?

Alkyl bromide

Phenol

Carboxylic acid

Alcohol (correct)

What is the key application of bioisosteres mentioned in the context?

Increasing tubulin inhibition Signup and view all the answers

Which combination is referred to as a prodrug in the content provided?

Irinotecan and its active metabolite Signup and view all the answers

What method is used to transform borane into alcohol?

Hydrolysis Signup and view all the answers

Which compound is a bioisostere listed in the content?

B(OH)2 Signup and view all the answers

In the reduction of alkynes, which of the following reactants is key for the hydroboration step?

B2H6 (diborane) Signup and view all the answers

What is the role of NaOH in the transformation of borane to alcohol?

Base Signup and view all the answers

What indicates a significant increase in tubulin inhibition for the compounds mentioned?

IC50 values Signup and view all the answers

What is the pKa value that corresponds to the thiol group RSH?

10 Signup and view all the answers

Which compound is classified as an example of a sulfonamide?

Sulfanilamide Signup and view all the answers

Which of the following statements about the bond lengths is correct?

C-S bond is shorter than S-S bond Signup and view all the answers

In terms of nucleophilicity, which compound is more nucleophilic than the others?

PhSNa Signup and view all the answers

Which of the following is a correct representation of a sulfoxide?

R-S-O Signup and view all the answers

What type of reaction occurs to prepare thiol from a halogenoalkane?

Nucleophilic substitution Signup and view all the answers

Which functional group has a higher pKa value than RSH?

Alkyl hydroxide Signup and view all the answers

Which compound contains a sulfonium ion?

Sulfanilamide Signup and view all the answers

What type of electrophilic species does sulfoxide represent?

Neutral molecule Signup and view all the answers

Which process yields R1SH from R1X using Na2S?

S-Nucleophilic attack Signup and view all the answers

What type of addition is most associated with sulfoxonium compounds?

1,4 Addition Signup and view all the answers

Which of the following represents a stronger nucleophile?

PhSeH Signup and view all the answers

Which reaction is characterized by syn-elimination?

b-elimination of sulfoxide Signup and view all the answers

Which compound is characterized as a soft nucleophile?

Sulfoxonium Signup and view all the answers

What is the outcome of base treatment of sulfoxonium compounds?

Formation of Ylides Signup and view all the answers

Which heterocycle is indicated to have a structure containing sulfur and nitrogen?

Thiazole Signup and view all the answers

What type of compound is selenocysteine classified as?

Amino acid Signup and view all the answers

Which oxidation method is properly matched with its product?

Wittig reaction to aldehyde Signup and view all the answers

The stronger nucleophilicity in chalcogenides is generally characterized by which compound comparison?

PhSeH > PhOH > PhSH Signup and view all the answers

Which of the following transformations is characterized by instability of selenoxides?

Hydrolysis Signup and view all the answers

What is a common application of diselenides in nucleophilic reactions?

Serving as reducing agents Signup and view all the answers

Which of the following reactions involves selenol as a nucleophile?

Addition to carbonyls Signup and view all the answers

Which selenide species is an electrophilic reactant?

(PhSe)2 Signup and view all the answers

What product is formed after the oxidative treatment of PhSeH with SeO2?

Selenoxide Signup and view all the answers

What is the primary biological function of glutathione peroxidase?

Preventing oxidative damage Signup and view all the answers

What type of chemical reaction does palladium-catalyzed cross coupling involve?

Carbon-carbon bond formation Signup and view all the answers

Which functional group is present in glutathion?

Tripeptide Signup and view all the answers

What type of compounds are boranes classified as?

Inorganic compounds Signup and view all the answers

What does the process of hydride transfer typically involve?

Transfer of a hydrogen atom with electrons Signup and view all the answers

Bortezomib is primarily known for its activity in which area?

Anticancer therapy Signup and view all the answers

What is the role of selenium in biological systems as mentioned in the context?

Functions in antioxidant enzymes Signup and view all the answers

What is the typical role of a nucleophile in a nucleophilic addition reaction?

To donate electrons Signup and view all the answers

Which of the following represents a common reactant in the Suzuki-Miyaura coupling?

Aromatic halide Signup and view all the answers

Which sulfur compound is mentioned in the context as part of the chemical reactions shown?

Sulfonic acid Signup and view all the answers

Which of the following drugs is known as an antiviral agent?

Trifluridine Signup and view all the answers

What is the primary role of DAST in fluorination processes?

Deoxyfluorination Signup and view all the answers

Which factor helps manage the fluorine ion's stabilization in water?

Fluoride-proton interaction Signup and view all the answers

Which method is employed for nucleophilic fluorination according to the content?

Diethylaminosulfur trifluoride (DAST) Signup and view all the answers

What type of drug is Celecoxib known for?

Antiinflammatory Signup and view all the answers

Which characteristic is noted for sulfonyl fluorides in fluorination reactions?

Ease of preparation Signup and view all the answers

Selectfluor is primarily used for which fluorination type?

Electrophilic fluorination Signup and view all the answers

What is the role of thermodynamic stability in fluorinated compounds?

Provides stability under reactive conditions Signup and view all the answers

Which of the following describes a characteristic of fluorouracil?

Anticancer drug Signup and view all the answers

What type of reaction is described by SuFEx?

Click reaction involving sulfonyl fluorides Signup and view all the answers

Study Notes

Sulfur Chemistry

Sulfur is a chalcogenide, meaning it is part of group 16 on the periodic table.
Key sulfur containing molecules include cysteine, taurine, sulfanilamide, penicillin, and omeprazole.
Sulfur atoms are more electronegative than carbon atoms, meaning they attract electrons more strongly.
The C-S bond is 1.81 å.
The S-S bond is 2.05 å.
Thiol (R-SH) is more acidic than an alcohol (pKa of 10 vs. 16) and has a stronger acidity than phenol (pKa of 8 for PhSH versus 9.9 for PhOH).
Thiolate (RS-) is a stronger nucleophile than phenolate (PhONa) and alkoxides (RONa).
Sulfoxide (R=S=O) and sulfone (R=SO2=R) are more stable than selinoxide (R=Se=O) and selinone (R=SeO2=R).

S-Heterocycle

Thiophene is a five-membered, sulfur-containing heterocycle.
Thiazole, benzothiazole, and imidazothiazole are other examples of sulfur containing heterocycles.

Selenium Chemistry

Selenium is a chalcogenide.
Selenium is less electronegative than oxygen and sulfur.
Selenium bonds are longer than sulfur bonds.
Selenoxides (R=Se=O) are more reactive than sulfoxides (R=S=O) and are easily generated from selenol (R-SeH).
Selenium can undergo rapid oxidation.
Organoselenium compounds are often biologically active, serving as antioxidants and anti-inflammatory agents.
Key selenium containing molecules include ebselen and selenocysteine.

Bore Chemistry

Boron has a valence of 3 electrons and its NMR signal is at 11 ppm.
Key boranes are BH3 and BR3.
Key boron containing molecules include boric acids (B(OH)3 ), boronic acids (R-B(OH)2), boronic esters (R-B (OR')2), and bortezomab (anticancer agent).
Boric acid is a weak acid.
Boron can be incorporated using palladium catalyzed Suzuki-Miyaura coupling.

Reactivity and Synthesis

Boron undergoes nucleophilic addition, hydride transfer, and alkyl transfer reactions.
Organoboron undergo reduction of alkenes and alkynes via hydroboration reactions.
Boranes can be oxidized to form alcohols, aldehydes, and ketones.
Boranes are useful for carbon-carbon bond formation via Suzuki-Miyaura coupling.
Boranes can be used to synthesize prodrugs.
Boranes are biologically active due to their ability to modulate enzyme activity.

Fluorination

In drug development, fluorination is used to modulate certain properties
Permeability is improved through hydrophoby
pKa is influenced by its electronegativity which affects potency
Fluorine is a hydroxyle/hydrogen isostere
Fluorine is used for positron emission tomography (PET) with 18F

Known Fluorinated Drugs

Fluorouracil is an anticancer drug
Celecoxib is an anti-inflammatory drug
Trifluridine is an antiviral drug

Nucleophilic Fluorination

Diethylaminosulfur trifluoride (DAST) is used for deoxyfluorination
DAST reacts with an alcohol to form a fluoride

Electrophilic Fluorination

Selectfluor is an electrophilic fluorinating reagent
Selectfluor reacts with a nucleophile to form a fluoride

SuFEx: Sulfonyl Fluorides (RSO2F)

Sulfonyl fluorides are used in a new Click reaction
Advantages:
- Ease of preparation
- High stability in water, even under acidic or basic conditions
- High reactivity with various C, N and O-nucleophiles
- Thermodynamic stability
Fluoride-proton interaction: Stabilizes the fluoride ion in water, allowing for chemistry in aqueous environments.

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Description

Explore the fascinating chemistry of sulfur and selenium, including their properties, key molecules, and unique bonding characteristics. This quiz covers essential concepts such as acidities of thiols, stability of sulfoxides, and various sulfur-containing heterocycles. Test your knowledge of these important chalcogenides and their applications in biochemistry.