Hydrocarbons Flashcards
Hydrocarbons
• Composed of carbon (C) and hydrogen (H)
• Constituents of fossil fuels, plastics, drugs, plants etc
• Occur diverse range of molecular structures and phases:
- Gases (methane, propane)
- Liquids (benzene)
- Solids (paraffin wax, naphthalene)
- polymers (polyethylene and polystyrene)
How are hydrocarbons divided
Aromatic
Aliphatic
>saturated=alkanes,linear or ring,all Bonds are single
>unsaturated=Alkenes or alkynes(c triple bond c),linear or ring,Have double of triple bonds
Displayed formula
Shows all atoms and all bonds present in the organic compound
Molecular formula
-number of each atom present,no information about bonding
Condensed formula
Similar to structural but no bonds shown
Skeletal/line formula
Most h are omitted and lines are c
Structural formula
-Shows the structural arrangement of atoms within a molecule.
-Not all bonds are shown and all atoms indicated using subscript
Alkanes
Simplest class of hydrocarbons
• Each carbon bonded to 4 other atoms
• When naming them, the suffix “ane” is used
• They have the general formula CNH2N+2 where N is an integer
General formula for alkanes
Cnh2n+2
Properties of homologous series
• The same general formula
• Similar chemical properties
• Show a gradual variation in physical properties, such as boiling point
• The difference in the molecular formula between one member and the next is CH2
Naming simple alkanes with substituents (alkyl group)
Step 1: Find the longest continuous carbon chain (parent chain)
Step 2: Identify the type of substituent attached to the parent chain
Step 3: Number the carbon chain so we have the most substituents (side chain) and lowest number at each substituent
Step 4: Write the full name as: number (position of substituent)- substituent name (for each group in alphabetic order) parent name
General formula for alkenes
• CnH2n for non-cyclic compounds
General formula for alkynes
CnH2n-2 for non-cyclic compounds
Functional groups
• Chemical motifs or patterns of atoms
• Display consistent “function”
• Part of hydrocarbon framework via covalent bonds
• Biomolecules contain many different types/combinations of functional groups • Affect structure, solubility and reactivity
7 functional groups
-alcohols
-amino acids(cook or nh2)
-ketone/aldehydes
-dna (phosphate group)
-DNA methylation(ch3)
-protein structure(sh)
Structure of an amino acid
Carboxyl and amine group
Side chain (rgroup)
Sulfhydryl group
-found in cysteine(amino acid)
-2 cysteine residues in close proximity to each other can form a disulfide bridge also called cystine.
-stabilise protein structure
Phosphate group
-sugar phosphate of dna
-charged
-acidic as it releases h+ irons into solution
Methyl Group
• From methane
• Hydrophobic and non polar
DNA methylation
• Change activity of DNA segment without changing sequence
Methylation and how it affects gene expression
Find out
Isomers
• Equal number of atoms of the same element
• Same molecular formula but different arrangement of atoms
• Different structures and properties
Structural Isomerism:
Chain
Positional
Functional group
Stereo-Isomerism:
Geometrical (cis-trans)
Conformational eg cyclohexane
Optical/enantiomers
Chain Isomerism
different arrangement of chain backbone
Consider the molecular formula C6H14
Position Isomerism
different position of functional group within chain
Consider the molecular formula C3H8O
Functional group Isomerism
different functional groups
Consider the molecular Formula C4H8O2
Cis-trans isomers
• Equal number of C and H atoms
• Inflexibility of double bond
• different orientations across a double bond
• Inflexibility of double bond
• Different spatial arrangements
• Geometric isomer –restriction rotation
Conformational isomers
• different orientations of a ring structure
• Rotation around single bond • Interconvert
Enantiomers
• non-superimposable mirror images of each other
• Asymmetric carbon –four different groups of atoms
• CHIRAL centre
How to identify enabntiomers
Shine plane polarised light and both enantiomers will rotate in opposite directions
Racemic mixture
Equal amount of both enantiomers
Pharmacological importance of enantiomers
-ibuprofen=reduces inflammation and pain
>s ibuprofen is the effective enantiomers and r ibuprofen is ineffective
-albutrol=relaxes bronchial airway muscles,improving airflow in asthma patients
> r abluterol is effective, s is ineffective
