3.3.1- Intro to Organic Chemistry (PAPER 2) Flashcards
What does IUPAC stand for?
International Union of Pure and Applied Chemistry (IUPAC)
This allows us to name organic compounds
What is the empirical formula?
The simplest whole number ratio of atoms of each element in a compound.
Eg- ethene is C2H4 but empirical is CH2
What is the molecular formula?
The actual number of atoms of each element in a compound.
Or the number of moles of each element in 1 mole of a compound.
Eg- butane molecular= C4H10, empirical= C2H5
What is the general formula?
The simplest algebraic formula of a member of a homologous series.
What is the general formula for alkanes?
CnH2n+2
n= number of C atoms
What is the general formula for alkenes and cyclic alkenes?
CnH2n
n= number of C atoms
What is the structural formula?
Shows the arrangement of atoms and the bonds between them if necessary- does not show all the bonds.
Brackets can show longer chains or branches.
Eg- C4H10= CH3CH2CH2CH3
OR CH3(CH2)2CH3
What is the displayed formula?
Shows the arrangement of ALL atoms in a molecule and ALL bonds between them
Eg- draw displayed formula for hexane- C6H14
What is the skeletal formula?
A ‘stick-like’ drawing that shows the bonds between carbon atoms only. Each ‘corner’ is a carbon atom!
Functional groups are shown, hydrogen and carbon atoms not shown.
Eg- draw the skeletal formula for C6H14
What are the characteristics of a homologous series?
A group of organic compounds ALL containing the same functional group.
Molecules from the same homologous series:
* Have similar chemical properties.
* Show a gradual change in physical properties.
* Can be represented by a general formula as they differ from one another by a -CH2
What is the suffix for alkanes and example of CH3CH2CH2CH3
suffix= -ane at the end
eg- butane
What is the prefix for branched alkanes and example of CH3CH(CH3)CH3
prefix= alkyl- at the beginning
eg- 2-methylpropane
What is the suffix for alkenes and example of CH3CH=CH2
suffix= -ene at the end
eg propene
What is the suffix for alcohols and example of CH3CH2OH
another example C4H10O
suffix= -ol at the end
eg- ethanol
another example= butan-1-ol: O attached to C, H attached to O
What is the suffix for aldehydes and example of CH3CH2CHO
suffix= -al at the end
eg- propanal
DOUBLE BOND BETWEEN LAST C AND O
What is the suffix for ketones and example of CH3COCH3
suffix= -one
eg- propanone
DOUBLE BOND BETWEEN MIDDLE C AND O: in-between alkyl group on left and right side.
What is the suffix for carboxylic acids and example CH3CH2CH2COOH
suffix= -oic acid
eg- butanoic acid
DOUBLE BOND BETWEEN LAST C AND O, C SINGLE BOND TO ANOTHER O AND H BONDED TO O
What is the prefix for halogenoalkanes and example CH3CH2Br?
prefix= fluoro-, chloro-, bromo-, iodo-
eg- bromoethane
What is the prefix/ suffix for cycloalkanes and example C5H10?
cyclo-……-ane
eg- cyclopentane (5C)
What are the IUPAC rules for nomenclature (naming) ?
1) Count the number of C atoms in the longest unbranched continuous chain- can go up or down as long as it is still C-C.
If C atoms form a ring, use cyclo- in front of stem.
2)Identify any branches/ functional groups or double bonds.
3) Count from the end that gives the lowest number to the functional group/double bond.
4) If the same groups appear more than once, give them a prefix: 2=di, 3=tri, 4= tetra
5) Groups/ branches are arranged alphabetically: eg ethyl before methyl
What is the order of importance for functional groups from highest to lowest?
- -COOH (oic acid) *
-CHO (aldehyde)
-C=O (ketone)
-OH (alcohol)
-triple bond
-double bond
-Cl, -Br, -F, -I (halogenalkanes)
-CH3, -C2H5, -C3H7, -C4H9 (alkyl groups)
What do commas and dashes separate?
Commas separate numbers,
dashes separate letters from numbers
Order of naming?
name stem- alkyl group prefix
1 meth- methyl= CH3
2 eth- ethyl= C2H5
3 prop- propyl= C3H7
4 but- butyl= C4H9
5 pent- pentyl= C5H11
What does a chemical mechanism show?
The movement of electrons during a chemical reaction.
How do we show the movement of a pair of electrons?
Through curly arrows- these always start from an area with electrons eg a double bond or lone pair.
Half headed arrow= movement of one electron
They point to where the electrons are being moved to/ the formation of a new bond.
What is a free radical? +example
A very reactive species which possesses an unpaired electron.
Eg- chlorine atom has unpaired electron and 2 electron pairs, bonds with other Cl atoms to form Cl2
Formed by homolytic fission of covalent bonds (equal splitting of electrons)
How do we represent the free electron in free radicals?
Using a dot ·
Eg ·CH3 (dot above C as it is free radical)
How to write the overall equation for free radical substitution?
1) For every H atom replaced by F/Cl/Br/I, one molecule of F2/Cl2/Br2/I2 is used and one molecule of HF/HCl/HBr/HI is released.
2) Number of H that are being replaced= number of halogen molecule needed= number of halide released at the end.
Eg- 6H replaced= 6F needed, 6HF released
Write the overall FRS equation for CHF2-CH3—–> CBrF2-CBr3
CHF2-CH3 + 4Br2—–> CBrF2-CBr3 + 4HBr
What occurs during initiation in free radical substitution?
When exposed to UV light, a molecule of halogen Cl2/Br2/F2/I2 breaks apart into 2 halogen atom free radicals- F· / Cl· / Br· / I·
Eg iodine: I2—–> 2I·
Draw the initiation of Cl2 using curly arrows
Cl:Cl 2 curly arrows from electrons, one to each Cl—- > Cl. Cl.
What occurs during propagation in free radical substitution?
Step 1) alkane/halogenalkane reacts with F· / Cl· / I· / Br· removing a H atom from the alkane/halogenalkane producing HF/ HCl/ HBr/ HI and a C based free radical.
Step 2) C based radical formed in step 1 reacts with F2/ Br2/ I2/ Cl2 to put an atom of F/Br/Cl/I on the C based free radical. This produces halogen free radical F· / Cl· / Br· / I·
Write the 2 equations for the propagation of CH3-CH2-CF3—> CH3-CHBr-CF3
1) CH3-CH2-CF3 + Br· —–> CH3-C·H-CF3 + HBr
2) CH3-C·H-CF3 + Br2 —– CH3-CHBr-CF3 + Br·
What occurs during termination in free radical substitution?
2 free radicals from end of propagation reactions collide together to form a molecule which stops the chain reaction.
Write the equation for the termination of CF3-CH2F in CH4—–> CF4
·CF3 + ·CH2F —-> CF3-CH2F
What is the overall free radical substitution reaction between chlorine and methane?
CH4(g) + Cl2 (g)—uv–>CH3Cl(g) + HCl (g)
What occurs in initiation of the reaction between chlorine and methane?
Cl2—–> 2Cl·
What happens in propagation of the reaction between chlorine and methane?
1) CH4 + Cl· —–> HCl + ·CH3
2) ·CH3 + Cl2 —-> CH3Cl + Cl·
What happens in termination of the reaction between chlorine and methane?
·CH3 + Cl· —-> CH3Cl
or
·CH3 + ·CH3 —> C2H6
or
·Cl + ·Cl —-> Cl2
How to separate the mixture of products?
Fractional distillation
What are structural isomers?
Compounds that have the same molecular formula but a different structural formula/ arrangement of atoms.
What are chain isomers?
Isomers that have different carbon chains- shorter/longer.
The molecules with more branching have lower boiling points.
Similar chemical properties, slightly different physical properties- straight chain isomers have higher boiling points as they can pack tighter together, branching decreases effectiveness of intermolecular forces less energy needed to separate molecules.
Draw and name all chain isomers of pentane: C5H12
methylbutane
dimethylpropane
What are position isomers?
When the functional group is attached to the carbon chain in a different location (on a different C atom).
Similar chemical properties, slightly different physical properties.
Same functional group.
Draw and name all position isomers of 1,1-dichloropropane
2,2-dichloropropane
1,2-dichloropropane
1,3-dichloropropane
What are functional group isomers?
Compounds with the same molecular formula which contain different functional groups.
Different chemical and physical properties.
What are the common functional group pairs?
Alkenes and cycloalkanes: eg C4H8 can be but-1-ene and cyclobutane
Aldehydes and ketones: eg C3H6O can be propanal and propanone
Carboxylic acids and esters: eg C2H4O2 can be ethanoic acid (COOH group) and an ester with a COOC group.
Alcohols and ethers: eg C3H8 can have O-H at end (alcohol) or C-O-C in the chain (ether)
Give equations to show how chlorine atoms catalyse the decomposition of chlorine.
.Cl + O3 —-> ClO. + O2
ClO. + O3 —-> .Cl + 2O2
