Functional Groups 5

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Questions and Answers

What characterizes atactic polystyrene compared to syndiotactic polystyrene?

It exhibits symmetrical molecular alignment.

It is completely amorphous. (correct)

It has a highly ordered structure.

It packs easily into crystalline domains.

What is a primary benefit of using polymers in pharmaceutical dosage forms?

They exclusively enhance drug solubility in water.

They can provide controlled release of a drug. (correct)

They are not compatible with excipients.

They always improve the taste of drugs.

Which type of polymer is used as a pH-dependent drug delivery platform?

Cationic polymers (correct)

Hydrophobic polymers

Anionic polymers

Neutral polymers

Which polymer is an example of one based on acrylic or methacrylic acids?

Eudragit E 100 Signup and view all the answers

What is one of the roles of cellulose-based polymers in pharmaceutical applications?

They can function as coatings for sustained release. Signup and view all the answers

What type of polymerization involves the reaction of bi-functional or multifunctional monomers to form longer oligomers?

Step-reaction polymerization Signup and view all the answers

Which of the following describes the process in chain-reaction polymerization?

Utilizes initiators to start polymer growth Signup and view all the answers

What is the defining feature of terminal alkynes?

They possess a C-C triple bond at the end of the molecule Signup and view all the answers

Which of the following statements about alkynes is incorrect?

Terminal alkynes are not acidic Signup and view all the answers

How are polymers commonly utilized in drug delivery?

By providing controlled release mechanisms Signup and view all the answers

What type of mechanism does a sulfonamide use to exert its action?

Blocking folic acid synthesis Signup and view all the answers

In the context of structure-activity relationships (SAR), which property is mostly examined?

The relationship between a compound's structure and its biological activity Signup and view all the answers

What application of methacrylic acids is most prominent in pharmaceuticals?

Their function as drug delivery systems Signup and view all the answers

What is a characteristic of copolymers?

They contain two or more different monomeric units. Signup and view all the answers

How does the molecular structure of a polymer influence its crystallinity?

It determines crystallinity by affecting arrangement and symmetry. Signup and view all the answers

In contrast to chain-reaction polymerization, what characterizes step-reaction polymerization?

Each step of the reaction is independent and involves different functional groups. Signup and view all the answers

What type of polymer is formed from the polymerization of styrene and methyl methacrylate?

Polystyrene(co-methyl methacrylate) Signup and view all the answers

What aspect of polymers is primarily affected by their size rather than their chemical properties?

Physical properties Signup and view all the answers

What common feature characterizes crystalline polymers?

They display a repeated geometric arrangement. Signup and view all the answers

Which term describes polymers that do not exist entirely in a crystalline form?

Semi-crystalline polymer Signup and view all the answers

What impact does crystallinity have on polymers during pharmaceutical processes?

It affects the diffusion and release rate of drug molecules. Signup and view all the answers

What is the general structure of an alkyne?

An alkyne contains a carbon-carbon triple bond. Signup and view all the answers

What are the acidic characteristics of terminal alkynes?

Terminal alkynes are acidic due to the presence of a hydrogen atom that can be removed as a proton. Signup and view all the answers

Name two types of polymerization methods mentioned.

Chain-reaction polymerisation and step-reaction polymerisation. Signup and view all the answers

What is the function of an initiator in chain-reaction polymerization?

An initiator enables the growth of a polymer chain by initiating the polymerization process. Signup and view all the answers

What are monomers in the context of polymer chemistry?

Monomers are the small repeating units that combine to form polymers. Signup and view all the answers

What distinguishes step-reaction polymerization from chain-reaction polymerization?

Step-reaction polymerization involves the reaction of bi-functional or multi-functional monomers rather than continuous chain growth. Signup and view all the answers

How are alkynes typically prepared from dihalides?

Alkynes can be prepared through hydrohalogenation of vicinal or geminal-dihalides. Signup and view all the answers

Describe one typical characteristic of polymers as macromolecules.

Polymers consist of very large molecules made up of many repeating subunits called monomers. Signup and view all the answers

What is generated when a mixture of two or more monomers undergoes polymerization?

A copolymer is generated. Signup and view all the answers

What is the role of an initiator in the polymerization process?

An initiator starts the polymerization process by generating free radicals. Signup and view all the answers

How does the size of polymers influence their physical properties?

The size of polymers significantly affects their physical properties, not their chemical reactivity. Signup and view all the answers

What are the two structural forms that polymers typically exhibit with regard to crystallinity?

Polymers exhibit regions of crystallinity and amorphous regions. Signup and view all the answers

What effect does molecular structure have on a polymer's crystallinity?

Molecular structure strongly affects a polymer's ability to crystallize. Signup and view all the answers

What type of polymer results from the polymerization of styrene and methyl methacrylate?

Polystyrene-co-methyl methacrylate is produced. Signup and view all the answers

What is the relationship between a polymer's molecular size and its crystalline structure?

Larger molecular size can hinder the formation of a regular crystalline structure. Signup and view all the answers

How do molecular symmetry and structure affect the packing of polymers into crystalline domains?

Highly symmetrical and regular molecular structures facilitate easier packing into crystalline domains, while irregular and amorphous structures hinder this process. Signup and view all the answers

What are the applications of acrylic or methacrylic acid-based polymers in drug delivery?

They are used to protect drugs, control their release, and can act as pH-dependent drug delivery platforms. Signup and view all the answers

Why is atactic polystyrene considered totally amorphous, and how does this affect its properties?

Atactic polystyrene lacks a regular molecular arrangement, resulting in amorphous properties that affect its mechanical strength and thermal behavior. Signup and view all the answers

What role do cellulose-based polymers play in pharmaceutical dosage forms despite being insoluble in water?

Cellulose-based polymers serve as tablet binders, coatings for sustained release, and emulsion stabilizers. Signup and view all the answers

What distinguishes syndiotactic polystyrene from atactic polystyrene in terms of crystallinity?

Syndiotactic polystyrene has a more regular and ordered molecular structure, which allows it to crystallize more easily compared to the amorphous atactic form. Signup and view all the answers

What is the primary mechanism through which sulfonamides exert their antibacterial action?

Sulfonamides act by interfering with folic acid synthesis, specifically by competing with PABA for the enzyme dihydropteroate synthetase. Signup and view all the answers

What was the original discovery of Prontosil related to its antibacterial properties?

Prontosil was initially discovered to have antibacterial properties in vivo, even though it showed no antibacterial activity in vitro. Signup and view all the answers

Explain the significance of para-aminobenzoic acid (PABA) in the action of sulfonamides.

PABA is crucial as it is a substrate for folic acid synthesis, and sulfonamides compete with it to inhibit this pathway. Signup and view all the answers

What does the term 'Structure Activity Relationship (SAR)' refer to in the context of sulfa drugs?

SAR refers to the relationship between the chemical structure of sulfa drugs and their Biological activity, helping to guide the design of more effective drugs. Signup and view all the answers

Why is it important to know which sulfonamide derivative is a stronger acid?

Knowing which sulfonamide derivative is a stronger acid can influence its pharmacological properties and stability in different pH environments. Signup and view all the answers

Describe the relationship between sulfonamides and the concept of prodrugs.

Sulfonamides illustrate the concept of prodrugs as they are inactive until converted to an active form (metabolite) within the body. Signup and view all the answers

How did the discovery of Prontosil impact the development of antibiotics?

The discovery of Prontosil marked a significant advancement in the development of antibiotics, paving the way for synthetic alternatives like sulfonamides. Signup and view all the answers

What role does the enzyme dihydropteroate synthetase play in the action of sulfonamides?

Dihydropteroate synthetase is the enzyme that sulfonamides inhibit by competing with PABA, thereby blocking folic acid production. Signup and view all the answers

Study Notes

Organic Functional Groups - Lecture 5

Alkynes are hydrocarbons containing a C-C triple bond.
A triple bond consists of one sigma bond and two pi bonds.
Terminal alkynes have triple bonds at the end of a molecule.
Acetylenic hydrogens are the terminal -CH groups.

Alkynes - Acidic Properties and Reactions

Alkynes are acidic, allowing the end hydrogen to be removed as a proton by strong bases like organolithiums or Grignard reagents.
This forms metal alkynides.
Alkynes are strong nucleophiles and bases.
They are protonated in the presence of acids.

Preparation of Alkynes

Vinyls or geminal-dihalides are used in the preparation of alkynes
Specific reaction with NaNH₂ gives the alkyne product.

Common Reactions of Alkynes

Alkynes can undergo hydration, halogenation, hydrogenation, epoxidation.
These reactions often involve addition or syn/anti addition mechanisms.

Introduction to Polymers

Polymers are large molecules (macromolecules) made up of repeating subunits called monomers.
Polymerizations are reactions that join monomers together.
Polymers can be natural (e.g., cellulose) or synthetic (e.g., plastics).

Chain-Reaction Polymerization

Polymer chain growth occurs solely through reactions between monomers and reactive sites on polymer chains.
Reactive sites are regenerated at the end of each step.

Step-Reaction Polymerization

Monomers (often bi- or multifunctional) react to form first dimers, then trimers, and finally long oligomers.
Often involve the formation of ester or other similar links.

Radicals in Vinyl Polymerization

Vinyl polymerization involves radical initiators.
Monomer adds to the growing polymer chain at the radical site.

Polystyrene, Acrylonitrile

Styrene polymerizes to form polystyrene.
Acrylonitrile polymerizes to another unknown polymer.

Copolymerization

Polymerization of a mixture of two or more monomers.

Step-Reaction Polymerization - Polyamides

Polyamides, exemplified by nylon, are formed from reactions between diamines and dicarboxylic acids.
Each reaction step is dependent on the other, more than one function group is in the monomers that cause the reaction to happen.

Structure and Properties of Macromolecules

Polymer size generally does not impact chemical properties.
Physical properties (e.g., crystallinity) differ significantly compared to smaller molecules.

Polymer Crystallinity

Crystalline polymers have regular, symmetrical structures with repeated geometric patterns.
Crystallinity is often incomplete, and they have regions of crystallinity and amorphous regions.
Crystallinity is categorized by the degree of crystallinity exhibited.

Crystallinity and Polymer Structure

A polymer's molecular structure strongly affects crystallinity.
Regular, symmetrical structures can pack easily into crystalline regions whereas non-regular structures cannot form crystals easily.

Polymers in Pharmacy

Polymers are used for drug protection, masking, controlled release, and enhanced bioavailability.
Cellulose-based polymers like cellulose, CMC, and hydroxypropyl cellulose are common in pharmaceutical applications.
Other polymers, (e.g., Eudragit E 100) can be used for pH-dependent drug delivery or to protect API from moisture.

Sulfa Drugs (Sulphonamides)

Sulfa drugs are synthesized from azo dyes.
Sulfa drugs inhibit folate synthesis.
Prontosil, a dye, has antibacterial properties in vivo but not in vitro.

Mechanism of Action (Sulfa Drugs)

Sulfa drugs are structural analogs to PABA and compete to be incorporated into the folic acid synthesis pathway.
Bacterial growth is inhibited by blocking the addition of PABA.

Structure-Activity Relationship (SAR)

The para-amino group is key for activity and must be unsubstituted (except for some acyl-derivatives)
Aromatic ring and sulfonamide functional group are needed, both connected directly to the ring.
The aromatic ring is substituted only in the para position.
The sulfonamide nitrogen must be primary or secondary
The R2 group is the only site variably placed to yield different effects.

Acidity of Sulfa Drugs

Different substituents can affect the acidity of sulfa drugs.

Clinically Active Agents

Data includes different half-lives and oral absorption rates for clinically used sulfa drugs.

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