Organic Chemistry Pt 1 - Week 7-9 Flashcards
(68 cards)
Molecular formula defintion:
Type and number of each element present
What 4 things must be specified when naming organic molecules?
- Carbon chain length
- Functional group class
- Any substituents present and where they are
on the molecule - Put everything together in alphabetical order
What is the priority order for functional groups?
Carboxylic acid — top priority
Ester
Acyl halide
Amide
Nitrile
Aldehyde
Ketone
Alcohol
Thiol
Amine
Ether
Alkene
Alkyne
Alkyl halide
Draw out 4-bromo-5-hydroxy-6-methylhepta-2-one
Longest chain is 7 –> hepta-
Principal group is C=O –> one ending
OH –> hydroxy
Br –> bromo
CH3 –> methyl
What are the 4 key physical properties of hydrocarbons?
States of matter: C1 - C4 gasses
C5 - C17 liquids
C17+ solids
Less dense than water
Molar mass increases with chain length
Boiling point - increases with chain length
- decreases with branching
What 4 factors are affected by increasing chain length?
- Increases bp
- Increases strength of van der Waals forces
- Increases Mr
- More likely to be liquid or solid at RT
Which linear molecules can contort into different conformations?
Alkanes can contort into different conformations –> due to rotation of bonds
Alkenes are frozen in a particular conformation
What are the two possible conformations of cyclic molecules and how do conformations occur?
- Chair
- Boat
Conformations have an energy difference so a particular conformation dominates at rt.
What are constitutional isomers (structural isomers) ?
- Chain isomers
- Position isomers
- Functional group isomers
How can you identify between geometric isomers?
Use E/Z or cis/trans system.
What are the 3 rules for assigning highest priority groups?
Higher atomic number = higher priority
If a group has to atoms of the same type bonded to the alkene follow the chain until a difference in priority occurs.
Bonds of a double bond are counted additively e.g. worth 2 single bonds same in an alkyne (‘worth’ 3 single bonds)
How does the E/Z system work?
Assign priority to each group on a C in the C=C
High priority on same side = Z
High priority on opposite side = E
How does the Cis/ trans system work?
Need each C to have one group in common
Same side = Cis
Opposite side = Trans
What occurs with the combustion of hydrocarbons?
Hydrocarbons combust to form carbon dioxide and water
Incomplete combustion forms carbon monoxide and water
What is a nucleophile?
electron donor, has an excess of electrons
Loves nuclei
What is an electrophile
Neutron donor, has and excess of neutrons
Loves electrons
What reaction do alkenes undergo?
React via electrophilic addition mechanism - due to nucleophilic C=C
Addition of X2 to form a dihaloalkane
Addition of H2 to form an alkane
What is markovnikov’s rule?
The major product forms from the addition of the (electrophile) H atom to the C with the most H atoms.
What conditions are required for the hydration of alkenes?
A small amount of concentrated acid as a catalyst - H3PO4 or H2SO4
What are the special characteristics of arenes?
Arenes have a special type of delocalisation that imparts special stability.
Alternating double and single bonds are conjugated with delocalised pi-electrons.
What are the 3 criteria for the Hukel criteria for aromaticity?
- The compound must be cyclic
- The atoms in the ring must be sp2
hybridised (have a free p-orbital) - The sum of the electrons contained in the p
orbitals must correspond to 4n + 2
electrons n= 0, 1, 2, 3 (2e-, 6e-, 10e-, 14e-)
What are haloalkanes?
Alkanes containing a halogen atom (F, Cl, Br, I)
Polar molecules have a permanent dipole at the carbon halogen bond
What are 3 haloalkanes that are commonly used as solvents?
- 1,2- dichloroethane
- dichloromethane (DCM)
- Chloroform
What are 4 reasons why haloalkanes are commonly used as solvents?
- have a moderate polarity compared to water
- able to dissolve most organic compounds
- Lower bp means easier to evaporate off
- DCM and chloroform are non-flammable
