UNIT 4 CHEM AFTER REACTION PATHWAYS

Macromolecules/Monomers/Polymers Definition

- Monomers: Small covalent molecules

- Macromolecules (polymers) is made when monomers are joined by covalent bonds

- Polymers,ers could be made from a single monomer or two or more different monomers.

Name the synthetic polymers, their monomers and examples:

Polymer: Polyalkene

Monomer: Alkene

Example: Polythene

Polymer: Polyester

Monomer: carboxylic and hydroxyl functional groups (ester)

Example: Polyester

Name the Natural Polymers, their monomers and examples:

Polymer: Polypeptide

Monomer: Amino Acid

Example: Protein, Enzyme

Polymer: Polysaccharide

Monomer: monosaccharides (sugars)

Example: Starch, cellulose (carbohydrates)

How is a Polyalkene Formed?

-Monomer is alkene

- Addition Reaction—> Double bond of each monomer breaks, and a new C-C bond is formed between two adjoining monomers until all monomers are used up.

-Examples include: Polypropene, Polyethene, Tetra Fluroethene

How are Polyesters formed?

• Formed By condensation Rections

• Esterification between carboxylic and hydroxyl function groups

• A new covalent bond is formed between C and O of the carboxylic and hydroxyl functional group respectively

• Byproduct of Water

• There are two ways for this to form, either:

  Both carboxyl and hydroxyl functional groups are present in two different molecules

  OR

  One molecule has two carboxyl function groups (dioc acid), and the other has two hydroxyl groups (diol).

• Reversible Reaction

How are Polypeptides formed?

• Monomer: Amino Acid

• The Amino Acid has a carboxyl functional group, an amino functional group and a hydrogen atom bonded to the same carbon atom

• The side chain(R) attached to the same carbon atom could vary.

• Condensation reaction take place between carboxyl functional group of one amino acid, and amino functional group of second amino acids.

• A peptide bond (amide bond) is formed between adjoining amino acid molecules

• For each peptide linkage formed, a water molecule is also formed

What is a monosaccharide

• Monosaccharide is a monomer molecule, also know as sugar

• The names do all monosaccharides end in “ose” Eg. Ketose, Aldose

• Chain structure is in equilibrium with cyclic structure in aqueous solution

How to name monosaccharides

In cyclic structure, the carbon atom next to the O atom (clockwise) is C(1) In glucose and galactose and C(2) in fructose and the OH group attached to it is;

• pointing down and opposite side to C(6) it is an Alpha isomer

• pointing up and same direction as C(6), it is a Beta isomer.

The three monosaccharides are:

• Glucose

• Galactose

• Fructose

How are disaccharides formed

• The condensation between OH group of C1 of the first monosaccharide and the OH group which is closest to it on the second monosaccharide.

• This bond formed is called a glycosidic bond

• The glycosidic bond is written in order of < alpha or Beta — atom number of the second sugar + glycosidic bond >

• Eg. alpha 1-4 glycosidic bond, Beta 1-4 glycosidic bond, alpha 1-4 glycosidic bond

• There are three types of Disaccharides;

• Maltose, Lactose and Sucrose

What is maltose

alpha glucose+ alpha glucose—> Maltose +H2O

Forms alpha 1–4 glycosidic bonds.

What is Lactose?

Beta-galactose + alpha-glucose—> lactose +H2O

Forms Beta 1-4 glycosidic bonds

What is Sucrose?

• alpha-glucose + Beta-Fructose—> Sucrose + Water

• alpha 1–2 glycosidic bond is formed between two monomers

• The beta fructose is inverted and switched sides to create this bond

What are Polysaccharides?

• A large number of monosaccharides (monomers) are joined by the glycosidic bonds

What are the two polysaccharides which make up starch?

• Amylose

• Amylopectin

Describe the properties of Amylose:

• Monomer is alpha-glucose

• alpha-glucose form alpha 1-4 glycosidic bonds in polysaccharide chain

• Only a few alpha glucose molecules per chain

• Unbranched, hence water soluble

• Intra chain hydrogen bonding form spiral shape in secondary structure

Describe the properties of Amylopectin:

• many alpha glucose molecules per polymer bonded through alpha 1-4 glycosidic bonds

• Branched polymer forming alpha 1-6 glycosidic bonds

• Branching doesn’t allow regular hydrogen bonds to form a spiral instead forms granules

• Since amylopectin is larger than amylose structure and branched, it is insoluble.

• Function: storage polysaccharide

Describe the properties of Glycogen

• large number of alpha glucose molecules per polymer chain

• Bonded through alpha 1-4 glycosidic bonds

• alpha 1-6 glycosidic bonds responsible for branching

• More extensively branched than amylopectin

• Water insoluble, suits function as storage polysaccharide

• Function: to maintain blood glucose and provide energy in muscle

Cellulose

• Unbranched hence linear polymer formed through beta glucose molecules

• Formed through 1-4 glycosidic bonds

• Inter chain hydrogen bonding forms between polymer chains to form microfibrils

• Function: This allows for cellulose to be rigid and give physical strentgh to plants, with some animals using cellulose as a form of energy