Unit 2.4 - Organic Compounds Flashcards
What IS organic chemistry?
The chemistry of carbon compounds
What’s another word for organic chemistry?
Carbon chemistry
How many carbon compounds are there?
Millions, with the number increasing daily
What do carbon compounds contain in general?
Hydrogen
Name 2 compounds that do contain carbon but aren’t considered carbon compounds
CO2 and carbonates
Why are CO2 and carbonates not considered to be carbon compounds?
They don’t contain hydrogen
What are some elements often found in carbon compounds?
Nitrogen
Oxygen
Halogens
Sulphur
Phosphorus
Why does carbon form so many compounds?
- Carbon is in group IV in the periodic table and has 4 electrons in its outer shell
When forming compounds, they’re covalent compounds
Carbon forms 4 covalent bonds in its compounds to achieve a stable electronic structure - Carbon forms strong covalent bonds with itself and hydrogen atoms - stable and resistant to oxidation and hydrolysis
Extremely high activation energy needs to be overcome
What are the C-C bonds that carbon forms found in?
Chain and ring systems
Describe organic reactions and explain why they’re like this
Generally slow
Poor yields
Extremely high activation energy needs to be overcome
Why are organic reactions slow and have poor yields?
Strong C-C bonds
What are the 4 different types of formulae we can use to represent organic compounds?
Molecular, graphic shortened and skeletal structural formulae
What does a molecule formula show?
The actual amount of atoms of each element in a molecule
Describe how molecular formulae are set out
Symbol for the element with subscripts to show how many of each atom in the molecule
In which order do we write the elements in a molecular formula?
C, H, O
then alphabetical
What do molecular formulae NOT show us?
HOW atoms are bonded
What is a graphic structural formula?
Displayed structural formula
What does a graphic structural formula show?
How elements are bonded and the types of bonds
What does a single line represent in graphic structural formulae?
A single covalent bond
What does a double line represent in graphic structural formulae?
Double covalent bond
How many bonds must carbon form? Describe these
4
Can be single, double or triple
With itself or other elements
What’s another type of bond that carbon forms and in what type of compounds are these formed?
Delocalised bonds
Aromantic
What type of bonds do aromantic compounds have?
Delocalised bonds
What type of compounds contain delocalised bonds?
Aromantic
What do shortened structural formulae show?
The graphic structural formula as a shortened structural formula
(Slightly different to molecular formulae)
What are skeletal structural formulae?
Shorthand representation of a compound’s molecular structure
Why are skeletal structural formulae useful?
Show complicated structures clearly
Quick and simple to draw
What’s implicit on a skeletal structural formula?
The location of the carbon atoms with hydrogens bonded
Where are carbon atoms implied to exist on skeletal structural formulae?
At each vertex (the second the pen touches the paper is one)
How do we figure out the number of hydrogen atoms from a skeletal structural formula? Why?
4 - (number of bonds drawn to that carbon)
Carbon has 4 covalent bonds
How do we represent hydrogen atoms bonded to non-carbon atoms in a skeletal structural formula? Give an example
Draw them explicitly
H bonded to O, for example
How do we signify all atoms that aren’t carbon or hydrogen on a skeletal structural formula?
With chemical symbols
Homologous series
Groups of related compounds
What’s the purpose of homologous series?
To make the study of the millions of carbon compounds easier
Draw the skeletal structural formula of propan-1-ol
(See notes)
Draw the skeletal structural formula of ethene
(See notes)
What’s ethene used for?
Used to make polymers
What’s ethanoic acid found in?
Vinegar
What type of acid is in vinegar?
Ethanoic
Name a compound used to make polymers
Ethene
Draw the skeletal structural formula of propene
(See notes)
Draw the skeletal structural formula of ethanoic acid
(See notes)
In which case does a tip of a skeletal structural formula not count as a carbon atom?
If it has a completely different element like OH attached to it
What do you call the members of the family in a homologous series?
Homologues
Homologues
All in the same homologous series
What do members of the same homologous series all have?
The same functional group
The same general formula
Similar chemical properties
Gradually changing physical properties
Functional group
An element or group of elements responsible for the chemical properties/behaviour of the compound in a homologous series
Provides a reactive site
What provides a reactive site in a homogenous series?
Functional group
What’s organic chemistry largely the chemistry of?
Homologous series rather than individual compounds
Alkane…
Functional group
Systematic name
Example
(N/A)
-ane
Ethane
Alkene…
Functional group
Systematic name
Example
C=C
-ene
Ethene
Halogenoalkane…
Functional group
Systematic name
Example
-Fl, -Cl, -Br, -I
Fluoro, chloro, bromo, iodo
Chloroethane
Primary alcohol…
Functional group
Systematic name
Example
-CH2OH
-1-ol
Propan-1-ol
Secondary alcohol…
Functional group
Systematic name
Example
CH(OH)
-2-ol
Propan-2-ol
Carboxylic acid…
Functional group
Systematic name
Example
-COOH
-oic acid
Ethanoic acid
Aldehyde…
Functional group
Systematic name
Example
CHO
-al
Propanal
Ketone…
Functional group
Systematic name
Example
-co-
-one
Propanone
Ester…
Functional group
Systematic name
Example
-COO-
-oate
Ethyl propanote
Do you count the C in COOH in carboxylic acids?
Yes
How many double bonds between carbon atoms to alkenes have?
At least 1
General formula of alkanes
CnH2n+2
General formula of alkenes
CnH2n
Which homologous series is ethane a part of?
Alkanes
Which homologous series is ethene a part of?
Alkenes
Which homologous series is Chloroethane a part of?
Halogenoalkanes
Which homologous series is propan-1-ol a part of?
Primary alcohol
Which homologous series is ethanol a part of?
Primary alcohols
Which compounds are part of the primary alcohol homologous series but don’t have the usual systematic name?
Methanol and ethanol
Which homologous series is propan-2-ol a part of?
Secondary alcohols
Which homologous series is ethanoic acid a part of?
Carboxylic acids
Which homologous series is propanal a part of?
Aldehydes
Which homologous series is propanone a part of?
Ketones
Which homologous series is ethyl propanoate a part of?
Esters
Describe the activity of alkanes
Largely inactive
Name 2 reactions in which alkanes actually do undergo?
Combustion
Cracking
Do alkanes have any double bonds? What does this mean for them?
No
They’re saturated
Give an example of a ketone
Acetone (nail varnish remover)
Name for carbon chain compounds
Aliphatic compounds
Aliphatic compounds
Carbon chain compounds
What are carbon chain compounds named after?
The parent alkane
What are the steps to naming an organic compound?
- Largest carbon chain is found - work out the parent alkane
- The functional group is found (going to be from the table)
- Any side groups (radicals) are found
- Assign a number to each carbon atom in the longest chain to find the position of the functional groups or side groups. Always use the lowest numbers possible.
What do we always use as the number for the positioning of the side groups in an organic compound?
The smallest number from the end
Parent alkane if the longest carbon chain is 1 carbon atom long
Methane
Parent alkane if the longest carbon chain is 2 carbon atoms long
Ethane
Parent alkane if the longest carbon chain is 3 carbon atoms long
Propane
Parent alkane if the longest carbon chain is 4 carbon atoms long
Butane
Parent alkane if the longest carbon chain is 5 carbon atoms long
Pentane
Parent alkane if the longest carbon chain is 6 carbon atoms long
Hexane
Name given to the side groups of organic compounds
Branching
What is the root name and radical of the side group of formula CH3?
Methane
Methyl
What is the root name and radical of the side group of formula CH3CH2?
Ethane
Ethyl
What is the root name and radical of the side group of formula CH3CH2CH2?
Propane
Propyl
Formula of radical methyl
CH3
Formula of radical ethyl
CH3CH2
Formula of radical propyl
CH3CH2CH2
Draw the skeletal structural diagram for 2-methylpropane
(See notes) - in the naming section
Draw the skeletal structural formula of 2-bromobutane
(See notes) - in naming section
Draw the skeletal structural formula of 2methylpropan-1ol
(See notes) - in naming section
Where do we place the number in the name of a compound when specifying the position of a double bond?
Between the word
When do we place the number between the word in an organic compounds name?
When specifying the position of a double bond
Do we count the carbon atoms in side groups?
No
When don’t we count the carbon atoms of a compound?
If it’s part of a side group
Draw the side group of a compound in skeletal structural formula, for example for 2-methylpropane
(See notes) - in naming section
Draw the graphic structural formula of trichloroethene
(See notes)
Um jw en Owen 96 gw en
F
What do molecular formulae of an organic compound not give information about in terms of atoms in a molecule?
Their arrangement
Isomers
Molecules with the same formula with different structures
Structural isomers
Have the same molecular formula but different structural formulae
What can structural isomers be found in?
Substances with the same functional group
Substances with different functional groups
Show the isomers of butane - what’s significant about them?
(See notes)
Both have the same functional group
Name substances that have isomers yet have different functional groups
Carboxylic acids and esters
What’s similar and what’s different between carboxylic acids and esters? Give an example
Same molecular formulae
Very different elements e.g -
Ethanoic acid - sour, bitter smell
Methyl methanoate (ester) - sweet smell
What do E-Z isomers appear in?
Alkenes
What type of bonds are significant in alkenes?
C=C bond
What are alkenes due to the C=C bond that they possess?
Unsaturated
What can single bonds do in a saturated molecule and what does this mean for them?
No double bonds - can freely rotate
Atoms in the bond are interchangeable
What cannot occur in unsaturated molecules with double bonds and why?
There is no free rotation due to the double C=C bond
The pi bond in an alkene prevents the rotation - we can’t interchange the atoms
What prevents the rotation of atoms in alkenes?
The pi bond prevents the rotation
Are alkenes saturated or unsaturated and why?
Unsaturated due to the presence of the double C=C bond
What type of isomers occur in alkenes?
E-Z isomers
E-Z molecules
Same old ulnar and structural formula,but different spatial arrangement of atoms
What’s an E molecule?
Both prioritised atoms on the different side of the double bond
What’s a Z-molecule?
Both prioritised atoms on the same side of the double bond
How do we remember that the prioritise atoms on a Z-molecule are on the same side?
“Zame zide”
What do we prioritise atoms in terms of when describing E-Z isomers?
Atomic mass
How did E-Z molecules get their name?
From the German…
E - entagen (opposite)
Z - zusammen (together)
What must each carbon atom on the double bond have in order to form E-Z isomers?
2 different groups or atoms
(e.g - Br and H)
What would imply that two isomers are NOT E-Z isomers?
2 atoms that are the same on the same side of the double bond
What are the 2 types of bond in the double bond in ethene?
Covalent bond
Pi bond
How does the covalent bond in ethene form?
By direct overlap of two orbitals
How does the pi bond in ethene form?
By the sideways overlap of two px orbitals
What do both the covalent bond and the pi bond result in?
A bond which can be imagined to be a charge cloud above and below the plane of the molecule
Draw a diagram to represent the nature of the pi bond in ethene
(See notes)
Draw the skeletal structural formula of 2-methylpropan
(See notes) - in naming section
Draw 2-2-dimethylbutane
(see notes)
What are the 3 types of reagents in organic chemistry?
Radicals
Nucleophiles
Electrophiles
When do radicals form?
When a covalent bond breaks
What is a radical reagent?
When a covalent bonds breaks, each atom/species retains one electron from the bond
The species which form are free radicals
Properties of radicals
Have an unpaired electron
Are very reactive, and react with other free radicals or atoms
Reactions involving free radicals are extremely rapid
Name 3 typical reactions that involve free radicals
Photochlorination of methane
Alkene polymerisation
Cracking and ozone depletion
Give 3 typical free radicals
Cl•
Cl3•
CH3CH2•
What is the symbol for a free radical?
•
(At the top)
What do you get when you crack a large alkane?
Free radicals
Hat can break up chlorine molecules into free radicals?
Ultraviolet light
What do some reagents that react with organic compounds seek out?
Centres of charge
Why do organic molecules often contain centres of charge?
Due to the presence of polar covalent bonds or pi bonds
Nucleophiles
Ions or molecules which can donate a lone pair of electrons, forming a covalent bond
What are Nucleophiles attracted to?
Positive changes or positive centres of charge
Give an example of a positive centre of charge
Nucleus
What’s polar in a Halogenoalkane and what happens to it therefore?
The carbon-halogen bond is poalr
The Nucleophiles will attack the positive carbon centre
Give some examples of typical Nucleophiles
OH-
Br-
CN-
H2O
NH3
Which part of a Nucleophiles attracts other molecules?
The lone pairs of electrons
How are Nucleophiles charged?
Either negatively or neutrally charged
Elctrophiles
Ions or molecules which can accept a lone pair of electrons, forming a covalent bond
What are electrophiles attracted to?
Negative charges or negative centres of charge
What is the centre of negative charge in an alkene?
The pi bond
What is the pi bond to an alkene?
A centre of negative charge
What will an electrophile attack in an alkene?
The centre of negative charge, which is the pi bond
Which homologous series gave centres of negative charge that electrophiles attack and what is this centre?
Alkenes
Pi bond
Give some examples of typical electrophiles
H+
NO2+
Cl+
How are electrophiles charged?
Positively
What are the 5 types of reaction?
Addition
Substitution
Elimination
Oxidation/reduction (redox)
Hydrolysis
What happens during an addition reaction?
2 molecules are brought together to produce 1 molecule
Give an equation to represent addition reactions
A + B —> C
What usually has to be available for an addition reaction to occur?
A double bond
What type of reaction usually requires a double bond in order to occur?
Addition reaction
What do alkenes always undergo? (Type of reaction)
Why?
Electrophilic addition
The C=C double bond is attacked
Substitution reaction
An atom or group of atoms replace another atom or group of atoms in a molecule
What normally has to be true after a substitution reaction?
The nature of the group which is introduces must be similar to that of the group which is replaced
Give an equation to represent a substitution reaction
AB + C —> AC + B
Give an example of a Nucleophiles substitution reaction
A hydroxide ion acting as a Nucleophile when it attacks the polar C-Br bond
Which reaction is an example of free radical substitution?
The photochlorination of methane
Why is the photochlorination of methane an example of free radical substitution?
Methane reacts with chlorine radicals
Elimination reaction
A simple molecule such as water is eliminated from the molecule
What often forms as a result of an elimination reaction?
A double bond
In which type of reaction is a double bond usually formed?
Elimination
What is an elimination reaction also known as if water is eliminated?
A dehydration reaction
Dehydration reaction
Type of elimination reaction where water is eliminated
Give an equation to represent an elimination reaction - what’s significant about this?
AB —> A + B
Opposite of addition reaction
What are the 2 things that usually form during an elimination reaction?
Organic molecule with double bond
Small molecule
Typical redox reaction example
Combustion
What does a redox reaction consist of?
Both oxidation and reduction - we can’t have one without the other
What rule can also be followed for determining which elements have been oxidised or reduced in a redox reaction as opposed to using OILRIG?
Oxidation
Gain of oxygen
Loss of hydrogen
Reduction
Loss of oxygen
Gain of hydrogen
What is oxidation in terms of oxygen and hydrogen?
Gain of oxygen
Loss of hydrogen
What is reduction in terms of oxygen and hydrogen?
Loss of oxygen
Gain of hydrogen
What occurs to primary alcohols in redox reactions?
Total oxidation
What happens to oxidising agents?
They’re reduced
Hydrolysis
Chemical reaction between the organic compound and water
Describe a hydrolysis reaction
Very slow and so usually require a catalyst
Common catalysts used in hydrolysis reactions
Sodium hydroxide
Hydrochloric acid
What type of hydrolysis reaction is one catalysed by sodium hydroxide?
Base catalysed
What type of hydrolysis reaction is one catalysed by hydrochloric acid?
Acid catalysed
What do empirical and molecular formulae show?
The ratio of atoms in the molecule
Actual number of atom in a molecule
What are the steps to writing an empirical formula?
Write symbols
Write masses/percentages from question
Divide each mass/percentage by the mass number of that element (Ar)
Divide each answer by the smallest number to find the ratio
(Do NOT round up/down ratios at the end - multiply everything up into whole numbers if they’re in decimals)
What do we NOT do at the end when working out empirical formulae and what do we do instead?
Round up/down
Multiply everything up into whole numbers
What are the steps to working out a molecular formula from an empirical formula?
Relative molecular mass (in question)
—————————————————. = a multiple
Mr of empirical formula
Multiply every atom of the empirical formula by this
What do we need to be given in the question in order to calculate the molecular formula from an empirical formula?
The relative molecular mass
How do we order the side groups in the name of a compound if there’s more than one of them?
Put them in alphabetical order
How are the particles held together in a solid?
Rigidly
How can the particles of a solid vibrate?
They’re rigid - can only vibrate around a fixed position
What must happen for a solid to melt?
Forces that hold it rigidly must be overcome
How are the particles in a liquid difference to those in a solid?
Less order, held together less rigidly and particles are further apart
What’s important about the particles of a liquid, even though there’s less order and they’re further apart than in a solid?
There;s still significant attractive forces to overcome when changing into a gas
What is needed to overcome the forces between particles in a solid or liquid when it melts or boiled?
Forces
How are the forces in a solid or liquid usually overcome to cause a substance to melt or boil?
Using energy, that’s usually heat/latent heat
How can we product which substance has the higher melting or boiling point?
Look at the strength of the forces between particles
What type of molecules are hydrocarbons?
Simple covalent molecules
What are the only things that hydrocarbons consist of?
Hydrogen and carbon atoms
Are hydrocarbons polar or non-polar? Why?
Non-polar
Electronegativities of carbon and hydrogen are similar
What’s the only type of force present in hydrocarbons and why?
Temporary dipole-temporary dipole (Van der Waal forces)
Hydrocarbons are non-polar
What’s significant about the Van der Waal forces in a hydrocarbon?
Weak intermolecular forces that require little energy to overcome
Where do Van der Waal forces act on hydrocarbons?
Between the surfaces of the molecules
When will the Van der Waal forces of molecules act more?
The more surface that’s in contact, the more the forces will act
What does more hydrocarbon surface in contact mean for their boiling point?
More surface in contact = more the forces will act
=more energy needed to overcome the forces
=higher melting and boiling points
What is the relationship between the amount of surface in contact between molecules and their boiling points?
More surface in contact = higher melting and boiling points
(Forces act more = more energy required to overcome the forces)
What’s the relationship between the amount of carbon atoms a hydrocarbon has and it’s boiling point? Why?
More carbon atoms = increased boiling point
(Van der Waal attractions increases)
What’s the relationship between the relate molecular mass of a hydrocarbon and its boiling point? Why?
Higher relative molecular mass = higher boiling point
(More carbon atoms = Van der Waal attractions increase)
What else can have an impact on the boiling temperature of a hydrocarbon apart from the chain length?
Branching
What effect do different structural isomers have on hydrocarbons?
Give them different boiling points
Why do different structural isomers of hydrocarbons give them different boiling points?
Difference surface areas are in contact for different isomers
What do more branches do to the shape of a molecule?
More branches = more spherical molecule
What happens to the amount of surface area for contact in molecules if spheres are packed together?
The surface area available for surface area contact is very small
What’s good about sausage shaped molecules?
Much more surface area available for surface area contact compared to spherical molecules
What effect does the branching of an isomer have on an isomer and why?
More branches = more like a sphere = surface area available for surface area contact is very small = weaker Van der Waal forces = lower boiling temperature
What type of hydrocarbons are often used in the oil industry and why?
Branched
More spherical = less surface area available for surface area contact = lower boiling temperature
Which group do alcohols contain?
OH group
What does the OH group in alcohols cause and what does this lead to?
Hydrogen bonds
Increased boiling point
Why does having an OH group in an alcohol lead to an increase in their boiling points?
Hydrogen bonds are formed, which are stronger than Van der Waal forces
What does having hydrogen bonds in a hydrocarbon lead to?
Increased boiling point
More soluble in water
Parent Alkane if the longest carbon chain has 7 atoms
Heptane
What’s the difference in naming the AMOUNT vs the POSITIONING of side groups on hydrocarbons?
di, tri… = the amount of side groups
2,3… (numbers) = the positioning of side groups
How would we show that the %’s of elements in an alkane are consistent with its formula?
Mr of formula
Ar (from formula) of each element divided by Mr - the %’s should match up
Which phrase should you always add at the end after describing which compounds have the lowest boiling point?
“so less energy is needed to separate the molecules”1
Free radial definition
A species with an unpaired electron
Why do chlorine radicals for but fluorine radicals don’t?
C-F bond is stronger than C-Cl bond
What must be true for E-Z isomerism to occur?
Both carbon atoms on the double bond must have 2 different groups or atoms
What do we need to show when drawing nucleophies?
Lone pairs of electrons
