Lecture 8. Fundamentals of Organic Chemistry Flashcards
What does a skeletal formula show ?
The skeleton of the molecular structure
What is a heteroatom ?
Non carbon
What type of structure are generally unreactive ?
Chains of carbon atoms attached to one another by single bonds (alkanes)
What are functional groups ?
Common groupings of atoms which react in characteristic ways
What does R stand for ?
Residue
What does the polarity of functional groups have an impact on ?
The acidity or basicity of the compound and its reactivity more generally
How is the extent of polarisation determined by ?
The difference in electronegativity between two elements
What polarises the c-x bond ?
Carbon being bound to a more electronegative element
What is the Bronsted and Lowry’s definition of acids and bases ?
An acid is a substance that donates a hydrogen ion.
A base is a substance that accepts a hydrogen ion.
What does acid-base reactions involve ?
Proton transfer
What is Ka ?
The acid dissociation for an acid
What is the formula for Ka ?
Products/Reactants
What is the formula for pKa ?
pKa = -log10Ka
What do strong acids have ?
Large Ka values and therefore small pKa values
What is the pKa of phosphoric acid ?
2.2
What is the pKa of imidazolium ion ?
6.9
What is the pKa of ammonium ion ?
9.3
What is the pKa of thiol ?
10.3
What is the pKa of B-keto ester ?
10.6
What is the pKa of water ?
15.7
What is the pKa of ketone ?
19.3
What is the pKa of ester ?
25
What is the pKa of carboxylic acid ?
4.8
What is the pKa of dihydrogenphosphate ion ?
7.2
What is the pKa of phenol ?
9.9
What is the pKa of alkylammonium ion ?
10.6
What is the pKa of alcohol ?
16
What is the pKa of thioester ?
21
What is lewis’ definition of acids and bases ?
An acid is an electron pair acceptor.
A base is an electron pair donor
How do molecules react in solution ?
- Molecules must diffuse through solution and encounter one another before they can react.
- When molecules approach one another, they must collide with enough energy to overcome intermolecular repulsion and with the correct orientation
What do polar reactions involve ?
The flow of pairs of electrons from areas of high electron densities to areas of low electron density
What is a chemical reaction that is considered spontaneous ?
Delta G is less than zero
How is Gibbs free energy related to the equilibrium constant ?
∆G = -RTlnK
What can the favourability of reactions be driven by ?
- Making enthalpy more negative
2. Making entropy more positive
What is the equation for Gibbs Energy ?
∆G = ∆H -T∆S
What is the symbol for enthalpy ?
Delta H
What is the symbol for entropy ?
Delta S
How would making the enthalpy more negative work ?
Breaking bonds requires energy and making bonds releases energy, so forming stronger, more stable bonds provides an enthalpic driving force
How would making entropy more positive work ?
- Increasing the number of particles increases the disorder of the system
- Solvation effects - localised charges can be strongly solvates, which orders the solvent which can contribute towards a lower entropy
What does the reaction mechanism show ?
The individual steps in chemical reactions
What do curly arrows show ?
The movement of a pair of electrons in reaction mechanisms
What is a nucleophile ?
Donor of electron pairs
What is an electrophile ?
An acceptor of a pair of electrons
