Polymers + hydrogen bonding Flashcards
What is polymerisation
process in which relatively small molecules, called monomers, combine chemically to produce a very large chainlike or network molecule, called a polymer.
Describe the process of making polymers by condensation
condensation polymerisation involves ejection of a small stable molecule e.g. HCl, CH3OH, H2O
What is a polymer
A polymer is a molecule which has a variable chain length
Describe the process of making polymers by addition
Addition polymerisation involves the addition of alkene monomers to a growing chain.
It is facilitated by a catalyst (E.g. Ziegler-Natta catalysts) (Ti, Zr, Hf or Al- based)
WHat are examples of condensation polymerisation
Polyamides and polyesters
What are examples of addition polymerisation
Polyethylene (H), polypropylene (CH3), polyvinyl chloride (PVC) (Cl), polystyrene (Phenol ring)
WHat sorts of polymer structures allow for polymers to be biodegradable?
Molecular structure closer to naturally occurring biopolymers make it easier for microorganisms to break them down.
What are some various functions of proteins
Provide structural shape and support (collagen)
Do mechanical work (actin and myosin)
Acts as catalysts or enzymes (carbonic anhydrase)
regulate body functions (hormones) (insulin)
Provide protection against disease (immunoglobulins)
Active in storage and transport (hemoglobin)
How are proteins formed
Proteins act as polyamides.
Amino acids condense to form a peptide (amide) link
Two amino acids condense to form a di-peptide and three amino acids form a tri-peptide etc. Proteins contain chains of >50 amino acids (up to >1000)
With 20 amino acids to choose from, there are a variety of proteins able to be formed
Basically proteins are polymers of amino acids
Can cis and trans peptide isomers be formed?
Yes
What are peptide bonds?
A peptide bond is a covalent bond that links amino acids together to form a protein.
What are the types of protein structures?
Primary structure
Secondary structure
Tertiary structure
Quarternary structure
What is the primary structure of a protein
It is the basic level and is the particular linear sequence of amino acids comprising one polypeptide chain
What is the secondary structure of a protein
It is the regular folding of regions into specific structural patterns within one polypeptide chain. H bonds between carbonyl oxygen and peptide bond.
The two most common secondary structural elements are alpha helices and beta sheets
local folded structures that form within a polypeptide due to interactions between atoms of the backbone
What is the tertiary structure of a protein
It is the 3D arrangement of all amino acids in a single polypeptide chain. This structure is usually conformational, native and actiev and is held together by multiple non covalent interactions
Overall 3D arrangement of its polypeptide chain in space. Stabilised by outside polar hydrophilic hydrogen and ionic bond interactions and internal hydrophobic interactins between nonpolar amino acid side chains
What is the quarternary structure of a protein
Specific spatial arranagement and instructions of proteins
Association of several protein chains or subunits into a closely packed arrangement. Each of the subunits has its own primary, secondary and tertiary structure. Held together by hydrogen bonds and van der waals forces between non polar side chains
How can knowledge of enzyme structure and mechanisms be used to benefit society?
Allows us to design inhibitors which can act as medicines.
Inhibitors have a similar chemical structure to the enzyme which will cause a negative effect and as a result they can block or distort the site of binding by the enzyme
E.g. penicillin inhibitting transpeptidase to kill bacteria
What is denaturing a protein
Denaturation implies the destruction of the tertiary structure of a protein molecule and the formation of random polypeptide chains.
How is denaturing a protein possible?
It is caused by the relatively weak intermolecular forces. Denaturing specifcally is caused by heat, changing pH or chemical reaction
Typically it is irreversible; alters biological and physical characteristicsG (e.g. less soluble)
Go more in depth about polymers
What are hydrogen bonds? How do they occur?
They occur when H is bonded to a very electronegative element such as (F,O,N), and as a result the bond is polar covalent.
This is one of the strongest intermolecular forces possible.
A hydrogen bond can be thought of as a bond between the hydrogen atom in one molecule and the lone pairs of the F,N or O atoms in another.
What are the common properties of F,O, N
They are the most electronegative elements
They are small (2s and 2p electrons in valence shells)
They have lone pairs
How do we draw H bonds
We indicate H bonds using a dotted or dashed line. The H bond is strongest when the bond angle is 180 degrees as this gets the excess negative charges as far away from each other as possible
Can hydrogen bonds occur in an intramolecular fashion?
Yes they can, even though they are typically considered a kind of intermolecular force. H bonds can occur between different functional groups within the same molecule as long as it is between H and either; F, O, or N
Are hydrogen bonds intermolecular. WHat is their nature?
Yes they are typically intermolecular bonds
Molecules with many O, N or F atoms may have multiple H bond sites. For example with formic acid (HCOOH), it can form a H bond “dimer”
What is the necessity for H bonds?
H bonds assist in holding DNA together.
I.e. H bonds between A and T, and also H bonds between C and G
What is the relevance of H bonds in DNA?
The double helical structure of DNA is supported by H bonds between complementary base pairs on the two intertwining strands
How many H bonds can a water molecule form?
up to four
Are molecules only limited to forming pairs of Hydrogen bonds?
No some molecules that form multiple H bonds don’t just only pair up, but they can actually form extended one- two- or three-dimensional networks
How are boiling points determined? (Discuss dispersion forces and hydrogen bonds)
Boiling points are directly correlated/related with the strength of the intermolecular forces.
Thus, stronger IMF such as hydrogen bonds will result in a higher boiling point. Additionally, if there is a molecule with increased electrons, it will typically lead to increased dispersion forces which further increases the strength of intermolecular forces –> bigger molecules have greater intermolecular forces.
Is a weaker or stronger IMF more likely to increase the surface tnesion
The stronger the IMF, the higher the surface tension
When the molecules of the liquid shrink into the minimum surface, then this tendency is known as surface tension. As the intermolecular forces increase, the area of space becomes less, and the surface tension increases.
What is surface tension
Surface tension is the property of surface of liquids which allow it to resist external forces, due to the cohesive nature of molecules.
Tension of surface film of a liquid caused by attraction of particles in surface by bulk of liquid which tends to minimise surface area
explain why concave meniscuses exist
Exist when the molecules in the liquid are attached to the glass more than to itself ii.e. water
explain why convex meniscuses exist
Exist when the molecules in the liquid are attracted more to the glass than to itself. i.e. mercury
What is capillary action/ capillarity?
Capillary action is the ability of a liquid to flow in narrow spaces without the assistance of, or even in opposition to, external forces like gravity.
What does capillary action rely on
Relies on the strong interaction between water molecules and the walls of capillaries
