Overview: Organic Chemistry

Question 1

Chemical Bonds Strong Bonds Intramolecular

Answer 1

Ionic Covalent (Metallic) Greater than >100kJ/mol

Question 2

Chemical Bonds Intramolecular Weak Bonds

Answer 2

Hydrogen (10-50 kJ/mol) Van der Waals <10kJ

Question 3

Electron shells Unfilled

Answer 3

Unfilled electron shells are unstable.

Question 4

Electron shells How do atoms get filled electron shells?

Answer 4

Accepting / Donating Sharing

Question 5

Ionic bonding

Answer 5

Accepting / Donating

Question 6

Convalent Bonding

Answer 6

Sharing

Question 7

What is Electronegativity

Answer 7

Measure of an atom’s ability to attract electrons in a molecule.

Question 8

What is electronegativity dependent on?

Answer 8

Strength of positive charge in nucleus Distance of bonded electrons (shielding from electron shells)

Question 9

Polar molecules Dipoles

Answer 9

Molecules with higher electronegativity draw the electrons closer to themselves and away from their neighbours.

Question 10

Van der Waals forces

Answer 10

Attractive or repulsive forces formed by dipoles Much weaker than covalent bonds Only work at short distances.

Question 11

Hydrogen Bonds Possible with dipole?

Answer 11

Possible with dipole where hydrogen bonds to a highly electrnegative atom.

Question 12

What is a dipole?

Answer 12

a pair of equal and oppositely charged or magnetized poles separated by a distance.

Question 13

Hydrogen Bonds Features

Answer 13

Relatively positive. Attracts negative atoms. Weaker than covalent bonds. Stronger than Van der Waals Vital for DNA and protein structure

Question 14

Ionic Bonds Summary

Answer 14

Donation of electrons from one (metal) atom to another (non-metal) to form positive and negative ions which then attract.

Question 15

Covalent Bonds Summary

Answer 15

Sharing of electron pairs (non-metals)

Question 16

Van der Waals bonds Summary

Answer 16

Weak attractions of covalent dipoles

Question 17

Hydrogen Bonds Summary

Answer 17

Attractions of covalent dipoles involving hydrogen covalently bonded to a highly electronegative atom

Question 18

Chemical bonds Summary

Strength equation

Answer 18

Question 19

What is molecular geometry?

Answer 19

3D arrangement of atoms in a molecule.

Affects reactivity, polarity, state of matter, colour, etc.

Electrons (bonded or free pairs) repel; they try to stay as far away from each other as possible.

Question 21

Molecular Geometry

3 Bonds

Answer 21

Planar

Question 22

Molecular Geometry

Four bonds

Answer 22

Tetrahedral

Question 23

Molecular Geometry

2 Bonds

Answer 23

Linear

Question 24

Molecular Geometry

When does bond rotation occur?

Answer 24

Only occurs around single bonds.

Less energetically favourable

Question 25

Carbon-based Life Advantages of Carbon

Answer 25

Abundant Versatile - 4 Valent Small Good bond strength Physical structure - chains

Question 26

Next best thing to use after Carbon?

Answer 26

Silicon

Question 27

Structure of H2O

Answer 27

"Bent" Polar molecule Hydrogen bonds lead to a lattice structure

Question 28

What is the Hydrophoic effect?

Answer 28

Not fully understood Engergetically unfavourable disruption of hydrogen bonding Hydrophobic elements aggregate to minimise disruption Effect tends to be stronger than Van der Waals or hydrogen bonds Hydrophoic effect is vital to protein structure

Question 29

Dissociation of Water H2O

Answer 29

H2O = H+ OH- Hydrogen ions can then bind to undissociated H2O to form hydronium ions (H3O+) H20 + H20 = H3O+ + OH- Water donates and accepts H+, so it is both an acid and a base.

Question 30

pH "power of hydrogen"

Answer 30

pH = -log10[H+] = log 1 / [H+] If [H+] = 1 x 10-^7, PH = 7 A change in pH of 1 represents a tenfold change in [H+]

Question 31

Acids, bases, buffers What is pH regulation vital for?

Answer 31

Biochemical processes

Question 32

Acids, bases, buffers Acids Hydrogen

Answer 32

Acids donate hydrogren ions; increase [H+]

Question 33

Acids, bases, buffers Bases Hydrogen

Answer 33

Accept hydrogen ions Decrease [H+]

Question 34

Acids, bases, buffers What do buffers do?

Answer 34

Provide small pH changes in response to moderate amounts of acid / base. Mixture of weak acid (HA) and conjugate base (A-) or weak base (B) and conjugate acid (HB+)

Question 35

Henderson-Hasselbalch Equation pKa

Answer 35

The lower pKa is, the stronger the acid. Weak acids have pKa in the range of -2-12

Question 36

Physiological Buffers

Answer 36

Bicarbonate: H2CO3 pKa - 6.1 Phosphate: H2PO24^2- pKa - 7.2 Proteins (Haemoglobin pKa - 6.6 - 8.2)

Question 38

Physiological Buffers Normal Human pH

Answer 38

Human 7.3 Plasma \<6.8 - \>7.8 may be fatal.