Chem T4 2022

Define A Synthesis Reaction

Using chemical reactions to produce (synthesise) a specific product

How Do You Determine A Reaction Pathway?

Retrosynthetic Analysis, considering side reactions and production of intermediates through the multistep process.

What is Retrosynthetic Analysis?

Working backwards from the desired product to choose reactants and pathways appropriately.

What Is A Contact Process?

Each step has its own reactants and products. Where the products from one reaction are the reactants for the next.

What Is A Linear Sequence?

One reaction is conducted after another.

What Is A Convergent Sequence?

Uses different reaction pathways, whose products are combined into another. i.e Two linear sequences converge into one.

How Does Reaction Efficiency Effect Yield?

Higher efficiency leads to a higher yield.

What Are Four Common Ways To Maximise Yield?

1. Removal of products
2. Recycling unused reactants
3. Conducting reactions under ideal conditions
4. Presence of Catalyst

What It The Goal Of Compromised Conditions?

To obtain the highest yield in the shortest amount of time for the least amount of effort / cost.

How Does Temperature Effect Reaction Rate And Yield?

Increasing Temperature Increases Rate as more particles will have sufficient energy

How Does The Type Of Reaction Affect The Optimal Temperature?

Higher temperature favours the Endothermic Reaction, hence, the temperature should be considered against if the reaction is Endo or Exo Thermic.

How Does Pressure Effect Reaction Rate And Yield?

Higher pressure increases the rate of production to the side with less total moles. So a higher or lower pressure should be used depending on which side (desired) has more or less moles.

How Do Catalysts Effect Reaction Rate and Yield?

Catalysts don't affect yield, but are used to speed up the rate of reaction. Helping the reaction to occur despite unoptimal conditions.

Describe the synthesis of Soaps

Formed by the alkaline hydrolysis of fats and oils by sodium / potassium hydroxide, boiled under reflux conditions. This breaks down triglycerides into 3 soap molecules and one glycerol molecule.

Explain the structure of soap and why it cleans

On one end is the polar carboxylate head with a Na or K atom attached, on the other is the non-polar hydrocarbon chain. The polarity of each end allows it to bind to both polar and non-polar molecules, leading to it's ability to clean.

Describe soap's mechanism of removal of dirt

The non-polar tails bind to and surround the dirt molecule, the polar heads then bind to water and get washed away.

What happens when soaps are lathered in hard water?

The Ca or Mg in the water combine with the carboxylate ions on soap, which forms an insoluble product, resulting in scum.

What are some key differences between soaps and detergents?

Detergents don't contain the carboxylate ion and therefore can't form the precipitate, the head of the tail is a SO3(-) ion, separated from the tail by a benzene ring.

What are most fuels made of?

Organic compounds, including coal, crude oil, carbohydrates, proteins and fats.

What is a biofuel?

A fuel produced from organic, renewable sources. e.g Ethanol, biodiesel.

Explain the Fermentation Process for Ethanol

Fermentation of Glucose; Grain / Fruit is mashed with water, yeast strain is added, mixture is kept at 37°C. The overall reaction is a REDOX where the carbon is reduced in ethanol and oxidized in CO2.

Explain the Hydration of Ethene

Thermal cracking is used to break long chains into small ethenes. In hydration, Ethanol isn't considered a biofuel because it is not from an organism and therefore not renewable.

Describe the synthesis of Biodiesel

Biodiesel can be produced from almost any fatty acid, it's an ester since it's a product from fats, which are triglycerides. The triglycerides react with short-chain alcohols to produce an ester, this is known as transesterification.

What is Atom Economy?

The ratio of desired products versus total products, represents efficiency of reaction.

What are the twelve principles of Green Chemistry

1. Prevent Waste
2. Maximize Atom Econ
3.Design less hazardous synthesis
4. Design safer products
5. Use safer solvents and reaction conditions
6. Increase energy efficiency
7. Use Renewable products
8. Avoid using chemical derivatives
9. Use catalysts
10. Design chemicals that will degrade
11. Prevent pollution
12. Minimize accident potential.

What is polymerization?

A process where monomers join together into large chains of repeating units.

What is addition polymerization?

All atoms in the monomer are used during polymerization.

What is condensation polymerization?

Monomers join with the expulsion of a small molecule. Not all original atoms are present in polymer.

What is a natural polymer?

naturally occurring, made from cellulose and proteins.

What is a synthetic polymer?

Able to be shaped and molded during production, plastics

What are thermoplastics?

Can be repeatedly melted and reshaped, the polymer chains are held together by weak intermolecular forces, most are addition polymers.

What is a thermosetting polymer?

Plastics that don't melt, but char on heating and must be shaped during manufacture.

What is a copolymer?

A polymer made of two different monomers in an alternating manner.

What are properties of Amorphous Polymers?

The molecular chains are randomly jumbled and don't exhibit a solid structure, this leads to crosslinking, giving room for stretching and bending. When the chains are pulled, the crosslinks stretch and return to their original position.

What are properties of Crystalline Polymers?

Molecular chains are organized and fixed, giving a hard structure.

How are Addition polymers prepped?

Usually by free radical process involving high pressure, temp and catalyst, which is often an organic peroxide which readily breaks up to form free radicals which initiate a chain reaction.

When are brackets used in polymer names?

When the polymer is more than one word, or begins with a number.

What do dicarboxylic acids and diols synthesize?

Polyesters

What do dicarboxylic acids and diamines synthesize?

Polyamides

What do multiple amino acids synthesize?

Peptides

What is a protein?

a polypeptide chain, hydrogen bonding can occur between chains.

Describe Plasticizers

usually a high boiling liquid that fits between the polymer chains, separating them from one another. Acting as a lubricant to weaken the attraction between polymer chains.

Describe Thermoset Polymers

Initially melt, but harden on further heating. Once formed they can't be remolded or recycled. On heating, the polymers become crosslinked with form a rigid network.

What is a High-Density Polymer?

Linear polymers with chains that can pack closely together, these are often quite rigid.

What is a Low-Density Polymer?

Branched-chain polymers that cannot pack together as closely as high-density polymers. There is often a degree of crosslinking, these are more flexible than high density polymers.

What are characteristics of Carbohydrates?

energy containing molecules built from monosaccharides, consisting of C, H and O

What are the three main Monosaccharides?

Glucose, Galactose and Fructose

What is Sucrose?

A Disaccharide made of Glucose and Fructose

What is Maltose?

A Disaccharide made of Glucose and Glucose

What is Lactose?

A Disaccharide made of Galactose and Glucose

What is the Polysaccharide Starch?

Made of glucose sub-units, it is a plant energy storage molecule. Starch and glycogen (similar molecule in animals) can be digested by animals.

What is the Polysaccharide Cellulose?

Glucose sub-units with different bonding than starch. It's a structural component in plants and cannot be digested by animals.

What is the Polysaccharide Chitin?

Glucose sub-units partly derived from non-sugars (nitrogen), that composes the exoskeletons of insects. Similarly bonded to cellulose.

Describe the general amino acid structure.

When amino acids polymerize, they expel water and become known as peptides.
Different amino chains can link together which lead to many ways of assembling chains.

What is the difference between a protein and a peptide?

A protein is longer and a peptide is a shorter chain of amino acids.

What is an enzyme?

Proteins linked together in one or more polypeptide chain that are able to catalyze chemical activity.

What is a Primary Protein Structure?

A single sequence of amino acid chain

What is a Secondary Protein Structure?

Proteins condense into a repeating pattern due to hydrogen bonding. Forms 2D structure.

What is a Tertiary Protein Structure?

3D folding pattern due to side chain interactions

What is an Essential Amino Acid?

Cannot be synthesized from scratch and must therefore come from diet.

What is a Non-Essential Amino Acid?

Can be synthesized fast enough by the body and isn't essential in diet.

What is a Conditional Amino Acid?

A non-essential amino acid that becomes essential under specific conditions.

What is an Isomer?

Compound with the same molecular formula but a different arrangement of atoms

What is a structural Isomer?

Same molecular formula but different structural arrangement

What is Stereo Isomerism and It's Types?

Same Molecular formula AND structure but arranged differently spatially. Geometric and Optical Isomerism

Why does Geometric Isomerism occur in non-cyclic alkenes?

The double bond restricts rotations which leads to isomerism.

What is Geometric CIS Isomers?

Functional Groups are on the SAME SIDE of the double bond

What is Geometric TRANS Isomers?

Functional Groups are on OPPOSITE SIDES of the double bond

How Do Geometric Isomers occur in Cycloalkanes?

The rigid structure (ring) of the cyclocalkane can prevent rotation, hence the formation of geometric isomers.

Do CIS or TRANS Isomers have higher melting points and why?

TRANS - They pack tighter and have higher intermolecular forces as a result which leads to a higher melting point as more energy is required to separate the molecules.

Do CIS or TRANS Isomers have higher boiling points and why?

CIS - They tend to be slightly polar which increases the dipole-dipole interactions which raises the boiling point.

What is a Chiral Molecule?

A Molecule that has no plain of symmetry.

What is an Optical Isomer? What is it's alternate name?

Two molecules are mirrors / asymmetrical. Same structure and shape but different spatial arrangement.

Also known as Enantiomers.

What are the physical and chemical differences between enantiomers?

All chemical and most physical properties are the same except they rotate the plane of polarised light in opposite directions.

How do chemical sensors treat enantiomers?

Most biological sensors are sensitive to shape and can therefore tell the difference between the isomers

What is the formula for frequency of EMR? What does this mean?

Frequency = Velocity / Wavelength
This means that as the wavelength decreases, the frequency increases

What are some applications of EMR?

Sterilization, treatment of cancers, gauge thickness of metal in steel mills.

What is Radiography?

Patients ingest a small radioactive source, which is located using a gamma camera.

Describe EMR Radio Waves

Can be absorbed by nuclei which cause their spin to change. Used by NMR spectroscopy to give information about chemical environments in a molecule.

Describe EMR Microwaves

Cause Molecules to increase their rotational energy, this can give info about bond lengths

Describe EMR Infrared

Absorbed by certain bonds, causing them to vibrate in different ways

Describe EMR Visible and UV Light

Produces electronic transitions which gives information about electronic levels within an atom / molecule.

Describe EMR X-Ray

Produced when electrons make transitions between energy levels, this can produce diffraction patterns which can be used as evidence for molecular and crystal structure.

What is the Degree of Unsaturation and how it is calculated?

Used to calculate the number of rings and pi bonds present in a structure. It is caluclated by (0.5)(2c+2-h-x+n) in compound CcHhNnOx

Describe Bonds and Unsaturation Levels

Double Bond is counted as one
Triple Bond is counted as two
A Ring is counted as one
An Aromatic Ring is counted as four

What is UV Spectroscopy? How does it work?

Study of absorption of UV radiation.
Valence electrons absorb the energy which excites the molecule.

What does Beer-Lambert's Law State?

That there is a linear relation between the concentration and the absorbance of the solution in relation to light. More concentrated = more light absorption.

What is a calibration curve?

Using known concentrations we can make a curve and use it to find concentrations of unknown samples.

How does IR Spectroscopy work?

A sample is bombarded with IR and the frequencies absorbed by the compound are recorded and a spectrum is produced. This gives info about present bonds and functional groups. Absorbed frequencies appear as troughs.

What do Diatomic or Polyatomic molecules undergo in IR spectroscopy.

Diatomic undergo stretching
Polyatomic can either stretch or bend.

Define the fingerprint region

To the right of 1400 a specific and unique frequency absorption can be used to identify specific compounds.

What is mass spectroscopy?

Uses a small sample to determine info about substance and present isotopes in a sample. Used for fossil dating and drug testing in sports.

How does mass spectroscopy work?

The sample is vaporized, then sent speedily through the machine and deflected by an electromagnet. Different sized atoms, molecules, fragments will deflect more or less depending on their size. Smaller molecules deflect quicker and easier.

What is organic fragmenting in Mass Spec?

Organic molecules will fragment into smaller pieces, the largest amu value represents the mass of the total molecule.

What is chemical fragmenting in Mass Spec?

In pure elemental compounds, the different peaks represent different isotopes of the same element and their % abundance.

What is NMR?

Nuclear Magnetic Resonance, it uses radiowaves which change the spin of nuclei.

Why are Radiowaves used in NMR?

Radiowaves don't have sufficient energy to affect electrons and chemical bonds.

What information does NMR provide about molecules?

The Number of H on C in chain (Low Res Peaks)
The Number of H on Neighbouring C in chain (High Res Peak)

How does NMR Spectroscopy work?

It magnetically aligns nuclei which absorb radiowaves and move into a higher energy state (beta). Eventually this is lost and the nuclei return to alpha (ground) state.
The energy difference is characteristic and allows determination of nuclei.