ATOMS + ATOMIC STRUCTURE
- Electronic Structure of Atoms
- Electron shell configuration
- Octet Rule
1s 2s 2p 3s 3p 3d 4s 4p 4d 4f 5s 5p 5d 5f 6s 6p 6d 7s 7p
Octet Rule: Atom always strive to have 8 valence electrons
ATOMS + ATOMIC STRUCTURE
- Molecular Bonding
- Covalent, Ionic, Hydrogen, Dipole-Dipole, Van Der Waals
- Electronegativity
Covalent: Atoms share electrons
Ionic: Transfer of electrons
Hydrogen: Weakly bonds atoms together, H
bonds with O, F or N
Dipole-dipole: Weaker than H-bond
Van Der Waals: Forces between same molecules ie. Dipole dipole, H bond, dispersion
Electronegativity:
<0.2 = non polar covalent
0.3-0.4 = polar covalent
>1.5 = ionic
ATOMS + ATOMIC STRUCTURE
- Lewis Structure
- involves sharing of 1 or more electrons between atoms
- staisfy Octet Rule
- multiple bonds can be formed
- electrons that don’t take part = lone pairs
Rule:
- Find total e, subtract 1e for every +ve charge
- Decide on central atom (least e-ve, not H)
- Assign leftover e to other atoms
- Leftover = central atom (exceed octet= double bond)
ATOMS + ATOMIC STRUCTURE
- Resonance Structures: Formal Charge
- electron pair delocalisation
- more than one possible structure for ALTERNATE SINGLE DOUBLE bond arrangement
- Formal charge
= #Ve in free atom - #Ve in bonded atom
ATOMS + ATOMIC STRUCTURE
- Polar + Nonpolar molecules
- electronegativity affects parent geometry
- will not affect VSPER
- happens due to net dipole movement
- can learn about solubility (net dipole)
CHEMICAL EQUILIBRIA
- Predict acid and base strength
strong acid:
- dissociates completely in aqueous solution
- usually have 1 H only
- eg. HCl, H2SO4, HBr, H2PO4, HNO3
weak acid (Ka):
- doesn’t completely dissociate
eg. CH3OOH, HNO2, H3PO4
strong base
eg. NaOH, KOH, CaO, Mg(OH)2
weak base
eg. NH3, C5H5N
- conjugate acid and base
Equations:
pH = -ln[H3O+]
pOH = -ln[OH-]
Kw = [H3O+][OH-] = 10^-14 at 25 C
CHEMICAL EQUILIBRIA
- Postion of equilibrium in acid base reactions
K«0.001
- only reactants present at eq.
- essentially no reaction occurs
- 001>1000
- only products are produced at eq.
- reaction goes essentially to completion
CHEMICAL EQUILIBRIA
- Calculate pH, pKa, pKo using Ka and Ko
- Apply Henderson-Hasselbatch equation to understand pH buffers
[H3O+][A-] = [HA]
Ka = [H3O+][A-]/[HA] [H3O+] = Ka ([HA]/[A-]) -ln[H3O+] = -ln(Ka [HA]/[A]) pH = -ln(Ka) - ln([HA]/[A])
pH = pKa + ln([HA]/[A])
FUNCTIONAL GROUPS
- Ethers
- Ketones
- Aldehydes
- Amines and Amides
- Saturated and Unsaturated
Ethers: methoxymethane, ethoxymethane
Ketones: propanone
Aldehydes: butanal
Amines: propan-1-amine (NH2)
Amides: propan-1-amide (CONH2)
Primary carbon: bonded to 1 C … etc
Saturated = C - C Unsat = C = C
Prefix = # of C atoms in parent Infix = nature of C-C bonds Suffix = class of compound
CHIRALITY
- Constitutional Isomers
- Stereoisomers
- Enantiomers
- Diastereoisomers
- Meso compounds
Constitutional:
- Same molecular formula
- Have different connectivities
- Different physical + chemical properties
Stereo (spatial isomers):
- Same connectivities
- Different spatial arrangement
- # of stereo isomers = # of chiral carbon centres * number of times molecule can rotate
Enantiomers:
- stereoisomers
- pairs of chiral molecules
- no mirror image, not superimposable
Dia:
- stereoisomers
- not mirror images
- can’t be superimposed
- have at least 2 chiral centres
Meso compounds:
- all meso compounds are dia
- are achiral
- mirror image is within itself
- superimposable upon folding itself
CHIRALITY
- E/Z isomerisation
- R/S chiral configuration
- E/Z = cis and trans via molecular weight (priority)
- E = trans, Z = cis
- R/S = rotating of molecule
- lowest priority points away
- R = rectus (clockwise),
S = sinister (anticlockwise)
CARBOHYDRATE
- D and L configuration
D = OH on RIGHT of penultimate carbon
L = OH on LEFT of penultimate carbon
CARBOHYDRATE
- Penultimate Carbon
- Anomeric Carbon
- Anomers
- Hemiacetal: Reactions included
- Acetal
- Glycosides
Pyran and Furan -ose
Penultimate C:
- Second to last carbon on Fisher Projection
- Ensure that CH2OH is on the end of it
Anomeric C:
- C that is attached to OH and O in Hawthorn Projection + Chair Projection
Anomers:
- Beta anomer = CH2OH and OH group on anomeric C are in cis
- Alpha anomer = CH2OH and OH group on anomeric C are in trans
Hemiacetal:
alcohol + aldehyde/ketone = hemiacetal
C bonded to OH, H , OR and R group
Acetal:
C bonded to 2 OR groups, R group and H group
- More stable than Hemiacetal
Glycosides:
- Cyclic acetals are not in equilibrium with their open chain carbonyl-containing form
- Hence will not undergo mutarotation
Pyran = 6 sided ring structure Furan = 5 sided ring structure
CARBOHYDRATE
- Fisher Projection
- Hawthorn Projection: axial and equatorial
- Chair conformation
Fisher:
- flat suraface, cross like
Hawthorn:
- ring structure
axial = up/down, equatorial = horizontal
- larger group in equatorial = more stable, less likely to undergo mutarotation
Chair:
- bowtie
- more stable form for sugars
CARBOHYDRATE
- Mutarotation
- Optical rotation due to change in equilibrium between 2 anomers (alpha and beta of one sugar)
- first, break up bond between anomeric carbon and O, to create an OH in place of O, and O in place of OH
- O and H attached to anomeric carbon rotate
- bond reformed, OH on anomeric C now points down in axial position, H in equatorial
CARBOHYDRATE
- Reactions
hemiacetal = alcohol + ketone/aldehyde
glycosides = cyclic acetals that cannot undergo mutarotation due to instability of new form taken during process
1-4 glycosidic bond occurs between 1C and 4C
1-6 glycosidic bond occurs between 1C and 6C
such formations of di/poly sacch. form H2O
STRUCTURE OF BIOLOGICAL MOLECULES
- Naming Carbs
triose C3H6O3 tetrose C4H8O4 pentose C5H10O5 hexose C6H12O6 heptose C7H14O7 octose C8H16O8
Beta-N-glycosidic bond
the CH2OH group is in cis with OH on anomeric C
bond is between OH on anomeric C and N in the ring structure of another sugar
