O- Intro Flashcards
Displayed formula
chemical formula showing ALL BONDS in a molecule
- eg. C-O-H
Structural formula
chemical formula showing arrangement of atoms in a molecule
Skeletal formula
all C atoms represented as points & H atoms x shown
General formula
shows mathematical relationship between atoms in an element
Alkyne structure
R三R
Haloalkane
R-X (halide)
- eg. -C-Cl
Alcohol
R-OH
Aldehyde
O
ll
/ \
R H
Ketone
O
ll
/ \
R R’
Carboxylic acid
R-C=O
`OH
Amine
R-NH2
Nitro
R-NO2
Methyl
CH3
Ethyl
CH3CH2
Propyl
CH2CH2CH3
Isomerism
When molecules have the same chemical formula
but diff. chemical structures
Structural isomerism
Molecule w/ the same molecular formula
but diff. structural formula/ arrangement
3 types of structural isomerism
- chain
- position
- functional group
Chain isomerism
- structural isomers (same molecular formula)
- same functional groups
- diff. arrangements of C skeleton
Position isomers
- same C skeleton
- same functional groups
- functional groups at diff. C
Functional groups that always go at the end of C chain
- carboxylic acid
- aldehyde
(3. amine)
What is an isomerism reaction?
- reactant and product have the same molecular formula
- diff. arrangement of atoms
2 types of stereoisomerism
- optical
- geometric (E-Z)
What are stereoisomers?
- molecules w/ same structural formula
- but atoms arranged differently in space
How do we represent bonds in 3D?
- same plane- lines
- going backwards- dashed bond
- going forwards- wedged bond (triangular)
What do we call molecules that are mirror images to each other, but are different molecules at the same time?
Non-superimposable
What are optical isomers?
- enantiomers
- have a chiral carbon– 4 single bonds w/ 4 DIFF. GROUPS
- labelling: +/- ; D/L ; R/S
What is a 50/50 mixture of 2 enantiomers called?
Racemic mixture/ racemate
How do we test for optical isomers?
- R & S rotate in opposite directions in plane polarised light
– if R rotates clockwise, S rotates anticlockwise
Why do geometric isomers exist?
- ALKENES ONLY
- restricted rotation around carbon-carbon double bond
Naming E/ Z isomers
- Z= substituents of higher priority (higher Ar) on the zame zide
- E= higher priority substituents diagonally opposite
– if immediate atom on substituent same (eg. CH3 vs CH2Br), decide using second atom down the chain (H vs Br) ∴ Br= higher priority
Another way of saying E & Z isomers
Z- cis
E- trans
How would you show that a sample is the d isomer not the l isomer?
- pass plane polarised light thru a solution of each isomer
- one isomer would rotate the plane at the polarised light clockwise, the other isomer would rotate it anticlockwise
How would you show that a sample of lactic acid contained equal amounts of the d and l isomer?
- pass plane polarised light thru a solution of the isomers
- if both isomers are present in equal amounts, plane of polarised light should not rotate
Explain why cis and trans isomers of 1,2-dichloroethane do not exist.
C-C single bond can easily rotate
State characteristics of an homologous series (alkanes).
- same general formula
- same functional group
- chemically similar (react ~ way)
- trend in physical properties (eg. bp↑ as Mr↑)
- differ by CH2
