Organic Chemistry Flashcards
Functional group
An atom or group or group of atoms that largely determine the molecules properties and reactions
eg: -COOH, -OH & NH2
Hydrocarbon
A compound that contains carbon and hydrogen only.
eg. The alkanes, alkenes and alkynes
Homologous series
series of compounds with similar properties and the same general formula, in which each member contains one CH2 unit more than the previous member.
Structural isomer
A compound with the same molecular formula, but different structures
Alkanes
A saturated hydrocarbon with a general formula of CnH2n+2
Alkene
unsaturated hydrocarbon (one or more double bond present between carbons) containing one Carbon – carbon double bond, with the general formula CnH2n
Properties of alkenes
- Planar geometry C=C (120• bond angle)
- Burns in oxygen to produce CO2 and H2O
- Decolourise Bromine water (orange to colourless)
Properties of alkanes
- Tetrahedral geometry (bond angle of 109.5•)
- Burns in oxygen to produce CO2 and H2O
- Does not decolourise bromine water
Alkyne
An unsaturated hydrocarbon (one or more triple bond present between carbons) with the general formula CnH2n - 2
Properties of alkynes
- Linear geometry (180• bond angles)
- Burns in oxygen to produce CO2 and H2O
- Does decolour bromine water
Alcohol
Name ends in –anol
Contain one –OH (hydroxyl) group on the chain.
can be made by hydration of ethene or fermentation of glucose.
Alcohols can be classified as primary 1•, secondary 2• and tertiary 3•
Carboxylic acid
Name ends in –oic acid
The carbon in the carboxyl group is included in the name.
Carboxylic Acids have two oxygens attached. One with a double bond one as a Hydroxyl group.
Aldehydes
Aldehydes have the C=O bond at the end of the carbon chain, at C 1.
Aldehydes contain the —CHO (aldehyde) group and are named by replacing the last e with -al.
Ketones
Ketones are characterized by the presence of carbonyl group C=O in chain
They are named by replacing the last -e in the name of the corresponding alkane with -one.
Amines
Primary amines have the NH2 functional group
Primary amines are named by replacing the last -e in the name of the corresponding alkane with -amine.
An amine has the prefix amino
Amide
Amides contain the —CONH2 group.
Amide molecules have the suffix –amide and the prefix amido
Esters
Esters all contain the ester functional group —OCO—
The name of an ester is from the name of the alcohol, with the suffix -yl, followed by the carboxylic acid with the suffix -oate.
Haloalkanes
Alkanes can undergo substitution reactions by replacing one of their hydrogen atoms with a halogen atom to form a haloalkane
The prefixes fluoro-, bromo- and iodo- are used
trend of bond strength in alkanes
The strength of the dispersion forces between hydrocarbon molecules is greater
- The closer the molecules are to one another (more chains means further)
- The larger the molecules is more regions of charge to attract each other.
Which has a higher boiling point?
oct-1-ene or propene
Octene (C8H16) is a larger molecule than propene (C3H6) (more electrons) More dispersion forces are acting between its molecules overall
Therefore there is more electrostatic attraction between oct-1-ene molecules which require a greater amount of energy to disrupt bonds between its molecules.
Solubility of hydrocarbons
Water dissolves organic molecules by forming dipole-dipole attractions and hydrogen bonds with them.
•small alcohols, amides, Amines, aldehydes and carboxylic acids form H bonds with water
Which compound is more water soluble?
CH3CH2CH2NH2 or CH3CH2CH2CH2CH2CH2NH2? Explain.
CH3CH2CH2NH2
Both are capable of forming hydrogen bonds with water but because CH3CH2CH2NH2 has a shorter hydrocarbon chain so is more polar overall.
Therefore it will form stronger H-bonds with water, increasing it’s solubility.
Fuel
Fuels are substances with stored energy that can be released easily for use as heat or power
Complete combustion
Complete combustion is burning in an abundance of oxygen so that the fuel can completely react with oxygen
hydrocarbon + O2→ CO2 + H2O
Incomplete combustion
Incomplete combustion occurs when the supply of air or oxygen is poor. Water is still produced, but carbon monoxide and carbon are produced instead of carbon dioxide.
hydrocarbon + O2 → CO + H2O
hydrocarbon + O2→ C + H2O
Conditions for addition of alkanes
hydrogenation
Ni catalyst and 150•C temperature
ALKENE + HYDROGEN→ALKANE
Conditions for addition of alkenes
Steam
Conditions:
Phosphoric acid catalyst, 300•C and 60-70 atm pressure
ALKENE + WATER→ALKANOL
Conditions for substitution of alkanes
UV Light
ALKANE + HALOGEN —>
HALOALKANE +HYDROGEN HALIDE
Substitution reaction of haloalkanes
Haloalkanes can be passed through sodium or potassium hydroxide to produce alcohols.
The haloalkane react with the hydroxide ions (OH-) to produce alcohols.
Why can alkenes undergo additions but alkanes may not?
Alkanes do not undergo addition reactions. They are saturated molecules, with no double bond to break.
Alkenes undergo addition reactions because they have a double bond.
Fermentation of glucose steps
1) glucose dissolved in warm water in conical flask
2) yeast added to solution and cotton wool is used to plug the flask
3) flask left in warm area to ferment
4) reaction will produce bubbles during fermentation. finished when CO2 bubbles stop
uses of ethanol
Solvent in perfumes, inks and glues
Fuel
To make esters (used in food flavourings) Alcoholic drinks
Oxidation of primary alcohols
Primary alcohols are oxidized by a strong oxidizing agent such as acidified permanganate or dichromate solution to form aldehydes and carboxylic acids
Oxidation of secondary alcohols
Secondary alcohols are oxidized by a strong oxidizing agent such as acidified permanganate or dichromate solution to form ketones
Formation of esters (esterification)
Formed by reaction between Alkanol and carboxylic acid producing water as a
condensation reaction or esterification.
Requires concentrated H2SO4
Polymer
A “molecular chain” made up from many thousands of repeating units
Thermoplastic + properties
A type of polymer: • Chains loosely tangled together •No cross links • Low melting point • Can be remoulded
Example: plastic bags and clingwrap
Thermosetting + properties
A type of polymer: • Cross links between chains • Much higher melting points • Cannot be remoulded • Rigid and inflexible
Example: kitchen bench coverings, outer layer on flat pack furniture
Elastomers
A type of polymer:
• Can be stretched or deformed
• Regain their shape
• Only a few cross links
Example: rubber, which is “vulcanised” by adding sulfur
Low density polyethene (LDPE) properties
- Thermoplastic formed under high temp and pressure
- Made of branched chains, that don’t fit together well - AMORPHOUS
- Low melting point
- Soft and flexible
- Used to make carrier bags and Glad Wrap
High density Polyethene (HDPE) properties
Type of thermoplastic formed using a catalyst at much lower temperatures.
• Chains are not branched
• They fit together much better
• More crystalline and less amorphous.
• Forms a harder substance, used to make wheelie bins, classroom chairs, milk bottles etc
Explain why HDPE has a higher melting point compared to LDPE:
More energy required to break forces between HDPE chains because Chains of HDPE fit closer together so dispersion forces act over a closer distance making them stronger than the dispersion forces between LDPE
Bromine water test
Brown bromine, Br2, liquid is decolorized in an addition reaction with an alkene only.
