Chemistry 14-16 PDF

# Properties of Polymers ## Polymers - Any of a class of materials, either organic or synthetic, made up of multiples of smaller chemical units called monomers, or macromolecules, which are very massive molecules. - Many of the building blocks of living things, such as proteins, cellulose, and nucl...

# Properties of Polymers ## Polymers - Any of a class of materials, either organic or synthetic, made up of multiples of smaller chemical units called monomers, or macromolecules, which are very massive molecules. - Many of the building blocks of living things, such as proteins, cellulose, and nucleic acids, are polymers. ## Plastic - A material made of organic compounds that are malleable and can be molded into objects. - Plastics are typically synthetic or semi-synthetic polymers, which are substances made of many repeating units. - The word polymer comes from the Greek words "poly" meaning many, and "meros," meaning parts or units. - Plastics are polymers but not all polymers are plastic. ## Thermosetting Polymers - Is permanently hardened and cannot be re-softened by heat. - This is due to the fact that during the curing process, the polymer chains in thermosets go through irreversible chemical processes that form strong cross-linked chains. ## Structures ### 1. Linear Polymers - Long, straight chains of atoms or groups joined by a bond are known as linear polymers. - They are the most basic type of polymer and are composed of end-to-end links of repeating units called monomers. - Compared to branched polymers, linear polymers are often more rigid. ### 2. Branched Polymers - A polymer that has branches or side chains attached to its linear backbone. - The repeating units that make up the main polymer chains also make up the branches. ### 3. Crosslinked Polymers - Are polymers in which long polymer chains are crosslinked together to form a 3D matrix of interconnect polymer chains. More specifically, a polymer has been crosslinked when the entire portion of polymer has been exposed to the cross-linking method. ### 4. Networked Polymers - Are complex polymers that are heavily linked to form a complex network of three-dimensional linkages. These polymers are nearly impossible to soften when heating without degrading the underlying polymer structure and are thus thermosetting polymers. ## 2 Types of Polymers ### 1. Thermosoftening Polymers - Are polymers that, when heated, may change into different shapes. - One type of thermosoftening polymer is polyethylene. - This includes both highdensity and low-density polyethylene polymers. ### 2. Thermosetting Polymers - Is permanently hardened and cannot be re-softened by heat. - This is due to the fact that during the curing process, the polymer chains in thermosets go through irreversible chemical processes that form strong cross-linked chains. ## Copolymer - If a chemist is synthesizing a polymer utilizing two distinct starting monomers there are several possible structures. The four basic structures are: random, alternating, block and graft. - **Random copolymer:** if 2 monomers are randomly ordered. - **Alternating copolymer:** each monomer is alternated with the other to form an ABABABA..... pattern. - **Block copolymer:** more complex repeating structures are possible, for example AAABBBAAАВВВААА.... - **Graft copolymer:** created by attaching chains of a second type of monomer on the backbone chain of a first monomer type. ## Properties - **Heat Capacity:** The extent to which the plastic or polymer acts as an effective insulator against the flow of heat. - **Thermal Expansion:** The extent to which the polymer expands or contracts when heated. - **Crystallinity:** The extent to which the polymer chains are arranged in a regular structure instead of a random fashion. - **Permeability:** The tendency of a polymer to pass extraneous materials. - **Elastic Modulus:** Is the quantity that measures an object or substance's resistance to deformed elasticity when stress is applied to it. - **Tensile Strength:** The strength of the plastic. (the force that must be applied in one direction to stretch the plastic until it breaks) - **Resilience:** The ability of the plastic to resist abrasion and wear. - **Refractive Index:** The extent to which the plastic affects light as it passes through the polymer. - **Unreactivity:** Most polymers are not affected by air or water and many are not affected by chemicals that make plastic durable and safely contain and protect many substances. - **Resistance to Electric Current:** Most polymers do not conduct electricity, making them insulators. # Describe the Structure of Proteins, Nucleic Acids, Lipids, and Carbohydrates, and Relate Them to Their Function ## Biomolecules - Also called biological molecules. - Any of numerous substances that are produced by cells and living organisms. - The smallest functioning unit of biomolecules is a monomer (mono means 1). - Monomer + monomer = dimer (di means 2). - Polymer (poly means many). ## Carbohydrates - Formally known as saccharides. - The term carbohydrates is derived from the French term hydrate de carbone. - The major source of energy for the body. - The general empirical structure for carbohydrates is (CH2O)n. - The main function is to supply the cells with "instant energy". ### Classification of Carbohydrates 1. Monosaccharides 2. Disaccharides 3. Polysaccharides ## Monosaccharides - From the prefix 'mono' which means one, monosaccharides is the simplest sugar and the basic subunit of carbohydrates. - These compounds are white solid at room temperature. - The most common monosaccharides: 1. glucose (also called dextrose). 2. fructose/levulose or fruit sugar. 3. galactose (sugar in milk). ## Disaccharides - Consists of two monosaccharides that are chemically combined. 1. Sucrose: The sugar we use to sweeten coffee is a disaccharides, table sugar. 2. Lactose: milk sugar, made up sugars, galactose and glucose. 3. Maltose: 2 glucose molecules, malt sugar, is an intermediate in the intestinal digestion (ie, hydrolysis) of glycogen and starch, and is found in germinating grains (and other plants and vegetables). ## Polysaccharides - Polymer containing numerous monosaccharides monomers. 1. Starch: It is the chief storage form of carbohydrates in plants and the most important source of carbohydrate in human nutrition. 2. Glycogen: It is a polysaccharides that is similar to starch because it is also composed of alpha glucose units. It differs from starch since glycogen shows a higher degree of branching and is a polysaccharides that is made by animals. 3. Cellulose: The glucose molecules in cellulose chains are arranged in such a way that hydrogen bonds link hydroxyl groups of adjacent glucose molecules to form insoluble fibrous sheets. These sheets of cellulose are the basic components of plants. ## Proteins - Formally known as Polypeptides. - Proteins are polymers of amino acids. - Proteins are made up of the elements carbon, hydrogen, oxygen, nitrogen, and sulfur. - Proteins function as: Enzymes, Pigments and Steroid hormones. ## Amino Acids - Are the building blocks of proteins. ### Essential Amino Acids: 1. Valine 2. Isoleucine 3. Leucine 4. Lysine 5. Methionine 6. Phenylalanine 7. Threonine 8. Tryptophan 9. Histidine ### Conditional Amino Acids: 1. Arginine 2. Glutamine 3. Tyrosine 4. Cysteine 5. Glycine 6. Proline 7. Seine 8. Ornithine ### Non-essential Amino Acids: 1. Alanine 2. Asparagine 3. Aspartate ## Level of Structures ### Primary Structure - Refers to the amino acidsequence that makes up a protein. ### Secondary Structure - Refers to a pattern formed by certain portions of an amino acid sequence. ### Tertiary Structure - Describes the three-dimensional structure of proteins ### Quarternary Structure - Some proteins consist more than one fold of polypeptides ## Lipids - The chief concentrated storage form of energy forming about 3.5 % of the cell content. - Lipids are organic substances relatively insoluble in water but soluble on organic solvents (alcohol). - They are water insoluble molecules (hydrophobic or water insoluble molecules (hydrophobic or watering-fearing) that are composed of carbon, hydrogen and oxygen. - Functions: Storing energy, chemical changes, waterproof barrier, insolution. - Common Lipids: Fatty acids, Triglycerides, steroids, waxes ## Fatty acids - Are carboxylic acids (or organic aacids), usually with long aliphatic tails (long chains), either unsaturated or saturated. - **Saturated acids:** Lack of carbon-carbon double bonds indicate that the fatty acid is saturated. - **Unsaturated fatty acid:** is indicated when fatty acid has more than one double bond. - Most abundant: fats and oils. - **Fats:** Solid from temperature contain saturated fatty acids, Produced only by animals. - **Oil:** Liquids at room temperature and contain unsaturated fatty acids, Produced by plants. ## Steroids - Are another class of lipids whose molecules are composed of fused rings of atoms. The most important steroid is cholesterol. ## Waxes - Are lipids that come from the combination of a long chain alcohol and a fatty acid. ## Nucleic Acid - Are the genetic material of the cell and are composed of recurring monomeric units called nucleotides. - Each nucleotides is composed of three principal components: - 5-carbon pentise sugar (pentagon). - Phosphate group (circle). - Nitrogenous base (rectangle). - Describe the preparation of selected organic compounds. - Any of a large class of chemical compounds in which one or more atoms of carbon are covalently linked to atoms of other elements, most commonly hydrogen, oxygen, or nitrogen. ## Friedrich Wöhler - Working in Berlin in 1828, Wöhler mixed two salts (silver cyanate and ammonium chloride) in an attempt to make the inorganic substance ammonium cyanate. - To his complete surprise, he obtained a product that had the same molecular formula as ammonium cyanate but was instead the wellknown organic compound urea. ## Organic Chemistry - Is a branch of chemistry that deals with the study of the structure, properties, reactions and preparation of organic compounds. ## Acetylation - To prepare acetanilide. - In the lab, aniline is converted to acetanilide by replacing one hydrogen in its –NH2 group with a CH3CO-group. This reaction, called acetylation, is commonly done with acetic anhydride. If unavailable, acetyl chloride can be used with pyridine as a catalyst. ## Aniline - Is widely used in the chemical industry as a precursor to manufacture dyes, particularly for synthetic dyes. It is also soluble in water. ## Acetylene - Is mainly used as a fuel and a building block in organic synthesis. ## Claisen-Schmidt Reaction - To prepare Dibenzalacetone (Dibenzylideneacetone). - Aliphatic aldehydes and ketones, the a-hydrogen atom is acidic. This acidity allows them to react with aromatic aldehydes in the presence of a dilute base, leading to the formation of a, ẞ-unsaturated aldehydes or ketones. - This reaction is known as the Claisen-Schmidt reaction. For example, when benzaldehyde reacts with acetone in the presence of aqueous sodium hydroxide (NaOH), it forms dibenzalacetone through condensation. ## Dibenzalacetone - Is also a common ingredient in some sunscreens as it absorbs the harmful UV light. - Is insoluble in water, but soluble in ethanol. ## To Prepare P-Nitroacetanilide - p-Nitroacetanilide is an organic compound that contains two key functional groups: a nitro group (-NO2) and an acetamide group (-CONH2). To synthesize it, we need to modify acetanilide (which is acetylated aniline) by introducing a nitro group at the para position to the amine group. - p-nitroacetanilide mainly used for: - Dye synthesis (particularly for azo dyes). - Organic chemical synthesis as an intermediate. - Pharmaceutical industry for developing bioactive derivatives. ## Coupling Reaction - Preparation of 2-naphthol aniline dye. - 2- Naphthol aniline dye is a scarlet dye that can be prepared by coupling reaction. - Aniline reacts with sodium nitrite in the presence of hydrochloric acid to form benzene diazonium chloride. Further benzene diazonium chloride reacts with 2-naphthol forms a bright orange colour 2-naphthol and forms aniline dye. - 2-Naphthol aniline dye is a type of synthetic dye used in various industries, particularly in textiles, leather, and sometimes in paper. It is made from 2-naphthol (a chemical compound derived from naphthalene) and aniline (a type of amine compound).