S3.2: Functional Groups: Classificaiton Of Organic Compounds Flashcards
Définition of empirical formula
The simplest whole number ratio of the atoms in a molecule
Définition of molecular formula
The exact number of atoms of each element present in the molecule
Définition of structural formula
Spatial arrangement of all the atoms and bonds in a molecule
-> displayed/graphical formula
Condensed structural formula:
enough info to make structure clear
most covalent bonds omitted
-> double and triple shown
Identical groups bracketed together
Ex: CH3 CH2 CH2 CH2 CH3 -> CH3 (CH2)3 CH3
Définition of skeletal formula
Simplified displayed formula
All carbon carbon bonds -> lines
-> end of lines and meeting points = carbon atom
All hydrogen removed unless in a functional group
Used to show simplified organic formula by removing H from alkyl chains
Leave just C skeleton and associated functional group
Définition of stereochemcial formula
Attempts to show relative position and 3D geometry of atoms/groups of atoms around central carbon
Bonds in the plane of paper -> solid line
Bonds coming forward -> solid wedge
Bonds going backwards -> dashed wedge
What are functional groups?
Functional group:
-> determines the chemistry of an organic compound
One atom, group of atoms, or multiple bonds between C atoms
Own distinctive properties -> properties of compound government by function groups in it
Organic compound same functional group = same class
What is catenation?
The ability to form bonds between atoms of the same element
Special nature of carbon - catenation
Carbon -> 4 covalent bonds
C can form many carbon compounds because of the strength of C-C covalent bonds
Can form chains/rings with single,double,triple covalent bonds, bond with other atoms/groups
-> other group 14 can also do -> but chemistry is limited due to weaker bond strength
-> carbon = Goldilocks zone
What is a homologous series?
Organic compounds with the same functional group but a different number of carbon atoms
-> Same functional group -> similar chemical properties
What do all members of a homologous group have in common?
Members of homologous series: homologues
-> same general formula
-> formula of monologue differs from neighbor by CH2
-> same function groups
-> similar chemical properties
-> gradual change in physical properties
-> usually prepared by similar methods
Prefix for homologous series
1 - meth
2 - eth
3 - prop
4 - but
5 - pent
6 - hex
… etc.
What are the general trends in physical characteristics in a homologous series?
Generally:
Bp and mp increase with molecular size
-> increased strength of London dispersion forces
Similar trends with other properties:
Melting point, density, viscosity
What is IUPAC nomenclature?
IUPAC or systemic nomenclature can be used to name organic compounds and therefore make it easier to refer to them
How do you name alkanes?
General formula: Cn H2n+2
-> only single bonds -> saturated
(Number of carbon) + ane
If side chains present:
Position of group indicated by number the carbon atom in the longest chain starting the end that gives the lowest possible numbers in the name
Then add -to to normal prefix system
Ex: 3-methyl hexane
If multiple of same alkyl side chain/functional group:
Di/tri/tetra/etc. Added in front of name
Adjacent numbers have commas between them
Separate numbers from words with hyphen
Ex: 3, 3, 4 - Trimethyl hexane
If more than one type of alkyl chain:
Same numbering system
Different side chains in alphabetical order
Ex: 4 - ethyl - 2 - methyl hexane
How do you name alkenes?
General formula: Cn H2n
-> unsaturated
(Number of carbon) + ene
In molecules with chain of 4+ carbon:
specific C=C position
-> lowest number carbon atom participating in double bond indicated before -ene
Ex: but-1-ene
How do you name alkynes?
General formula: Cn H2n-2
-> triple bond -> unsaturated
(Number of carbon) + yne
In straight chain of 4+ carbon:
Positon of C triple bond needs to be specific
-> lowest number carbon atom participating in triple bond indicated before -yne
Ex: but-1-yne
How do you name halgenoalkanes?
General formula: Cn H2n+1 X
Use prefix chloro- bromo- iodo- and suffix -ane
Molecules of straight chain of 3 or more carbon:
Positons of halogen specificed
Number of carbon closest to halogen -> indicated before prefix
Ex: 2-bromopropane
If multiple halogen groups:
The positon and type of functional group must be given
Ex: 2 chlorine on C-1 and 1 on C-2
-> 1,1,2 - trichloroethane
How do you name alcohols?
General formula: Cn H2n+1 OH
-> OH is functional group
(Number of carbon) + ol
-> 2 OH present -> -diol
What are carbonyls?
General formula: Cn H2n O
-> functional group C=O
2 subcategories -> aldehydes and ketones
-> same carbon number -> isomers of each other
Similar functional group arrangement -> similar chemical reactions
Difference in chemistry due to reaction that:
involve H on aldehyde
Nature of R groups
C=O -> polar -> dipole-dipole attraction
-> higher bp than expected for small molecules
-> solubility in water for lower members
How do you name aldehydes?
Carbonyl group on end of chain -> aldephyde
Formula: RCHO
-> H written before to avoid confusion with an alcohol
(Number of carbon) + al
How do you name ketones?
Minimum of 3 carbons
General formula: RCOR
(Number of carbon) + one
Straight chain of 4+ carbon:
Numbering needed
Ex: pentan-2-one or pentan-3-one
How do you name carboxylic acids?
General formula: Cn H2n+1 COOH or RCOOH
-> functional group: COOH
(Number of carbon) + oic acid
What are isomers?
Compounds that have the same molecular formula, but different arrangement of atoms
One group of isomers -> structural isomers
-> same molecular formula, different structural formula
What are the three different types of structural isomerism?
Functional group isomerism
Positional isomerism
Branched chain isomerism
What is functional group isomerism?
Different functional groups result in the same molecular formula, leading to functional group isomers
Isomers have very different chemical properties -> different functional groups
These homologous series can be functional group isomers:
Alkenes and cycloalkenes
Alcohols and ethers
Aldehydes and ketones
What is positional isomerism?
Positional isomers arise from difference in the position of a function group in each isomer
-> functional group in different carbon atoms
Some organic compound described as having primary, secondary, tertiary structures:
-> relate to the number of carbon atoms the function group carbon is attached to
-> ol, diol, triol
What is branched chain isomerism?
When compounds have the same molecular formula, but their longest hydrocarbon chain is not the same
-> caused by branching
Isomers in amines
Amines -> different classification system
Classification based on number of alkyl groups attached to the nitrogen in the amine:
-> primary amine: N attached to one other C (or alkyl group)
-> amine
-> secondary amine: N attached to two other C (or alkyl groups)
-> di___amine
-> tertiary amine: N attached to 3 other C (or alkyl groups)
-> tri___amine
Go through picture flashcards
:D
