Chemistry U4 AOS 1

• Organic compounds

• T or F? An organic molecule can only be naturally produced 

• What is the total number of bonds a carbon atom can form?

Organic compounds are identified as those where carbon is covalently bonded to other atoms 

• Often this involves other carbon atoms, hydrogen, nitrogen, and oxygen 

• False. In organic molecule can either naturally or synthetically produced 

 

Carbon atoms have a valence electron number of 4 (4 electrons in its outermost shell)  --> meaning each carbon atom can form a total of 4 bonds 

• Saturated

• Unsaturated

• Saturated meaning it possesses only single bonds between carbon atoms (C-C bonds) 

• Unsaturated meaning it possesses at least one double or triple bond between carbon bonds 

• The bond strength of a particular carbon bond depends on the bond energy - what is the bond energy and what unit is it measured in?

• What factors influence bond energy? Explain them.

• energy required to break the chemical bond which is measured in kJ/mol

 

The are various factors that impact the energy of a chemical bond, including: 

• Bond length - the distance between the nuclei of two bonded atoms 

• The difference in electronegativity of the atoms involved 

• Size of the atoms 

 

--> the length of the bond will vary depending on the strength of the electrostatic attraction between the nuclei of the bonded atoms and their shared electrons 

--> The size of the atoms involved also impacts the bond length; where bonds between larger atoms are expected to be longer (and hence weaker bond strength) 

In general, bond energy (and hence bond strength) increases as the length of a bond decreases 

 

Electronegativity how strongly an atom attracts electrons towards itself 

--> Bonds formed between elements with larger differences in electronegativity form stronger bonds 

 

Chem ½ link (don't need to remember the specific reasons, just where electronegativity increases and decreases in the table) 

	Trend in electronegativity	Explanation
Down a group	Decreases	More electron shells, increased shielding (repulsion from inner electrons), greater distance from nucleus
Across a period (left to right)	Increases	Increase in nuclear charge (positive charge of nucleus – as number of protons increase)--> increased electrostatic attraction    Increase in electrons --> closer to full outer shell – attract electrons more strongly

For butanoic acid, can you draw/write it in:

• Structural formula

• Skeletal formula

• Semi-structural formula

• Molecular formula

• Empirical formula

• Homologous series

• Functional group

A homologous series is a ‘family’ of compounds that have: 

²  a similar structure 

²  a pattern to their physical properties 

²  similar chemical properties 

²  the same general formula 

• In homologues series, organic compounds in which each successive member differs by -CH₂- from the previous one  

 

A functional group is an atom or group of atoms that largely determine the properties of a molecule 

Write the stem name/prefix for the following number of carbons in a hydrocarbons:

1

2

3

4

5

6

7

8

• Alkyl group

• Are they considered as functional groups. Why/why not?

Alkyl group containing only carbon and hydrogen atoms (e.g. −CH3, −CH2CH3) 

• They are not considered as functional groups as FGs affect the chemical properties of a compound while alkyl groups only affect a molecule's physical properties ((including melting and boiling point) 

• Alkanes

• General formula

• Is it saturated or unsaturated. Why or Why not?

• Suffix

Alkanes are saturated hydrocarbons that only have single carbon-carbon bonds in their structures 

• It's general formula is C_nH_{2n + 2} (n represents the number of carbon atoms in the structure) 

• They are said to be saturated because each carbon cannot bond with any more atoms 

• The suffix (at the end of the name) of the alkane is –ane

• Alkenes

• Functional group

• General formula

• Is it saturated or unsaturated. Why or Why not?

• Suffix

Alkenes are the homologous series that contains unsaturated hydrocarbons that have at least one carbon-carbon double bond in their carbon chain  

• They contain the alkenyl functional group (C=C)  

• They have at least one degree of unsaturation (due to the carbon-carbon double/triple blond) - as the carbon atoms can potentially form new bonds with other atoms (by breaking the double bond) 

• The suffix (at the end of the name) of the alkane is –ene 

• It's general formula is C_nH_2n 

• Aromatic hydrocarbons/arenes

• Cycloalkane

• Cyclohexane + draw diagram

Aromatic hydrocarbons/arenes: are ring-shaped organic compounds with no terminal carbon made entirely of carbon and hydrogen – examples include cycloalkanes and benzene 

Cycloalkane: saturated alkanes arranged in a closed ring with no terminal carbon, with all carbon-carbon bonds being single bonds 

• Each carbon atom is bonded to 2 adjacent carbon atoms and two hydrogen atoms 

• 'cyclo' = ring 

• 'ane' - saturated hydrocarbon 

• It's general formula is C_nH_2n 

 

Cyclohexane: a cycloalkane with 6 carbon atoms joined in a ring  

• 'Hex' = 6 carbon atoms 

• It’s formula is C₆H₁₂ 

• Benzene

• Does it undergo the typical reactions of alkenes (addition reactions)?

• Draw a diagram of benzene

Benzene is a cyclic compound that has 6 carbon atoms in its ring structure, each bonded to one hydrogen atom and two adjacent carbon atoms 

• One electron from each carbon atom is delocalised and shared equally between carbon atoms in the ring, resulting in a very stable structure that will not undergo the typical reactions of alkenes (addition reactions) 

• Haloalkane

• Is there a polar bond in this molecule? Why/Why not?

Haloalkane organic compound that has a halogen functional group (element in group 17 of the periodic table which include chlorine (Cl), bromine (Br), fluorine (F), and iodine (I)) 

• The halogen atom replaces one or more H atoms attached to an alkane’s carbon chain 

• X - often used as a general representation of a halogen 

As halogens are more electronegative than carbon atoms, they have a greater tendency to attract the shared pair of electrons to their own nucleus -->  this results in a polar bond: 

• the carbon atom has a partial positive charge 

• whilst the halogen atom has a partial negative charge 

• Amide

• Draw it’s FG

• Suffix

• T or F? They are generally derived from ammonia

Amine organic compound with an amino functional group (−NH2) in replace of a hydrogen  

• It has the suffix '-amine' 

• True. They are generally derived from ammonia -->  a hydrogen atom may be removed from ammonia (NH3) to form an amino (or amine) functional group (−NH2)

How are different structures of amines defined by? Is it the same as alcohols?

Unlike alcohols, primary secondary and tertiary amines are defined by the number of alkyl chains attached to the nitrogen not the carbon

• Amides

• Draw it’s FG

• Primary amide

Amides are organic compounds that contain the amide functional group (–CONH₂)  

• Which includes a carbonyl group (C = O) attached to an amino FG – similar to carboxyl groups except replace the –OH with the –NH2 

• Primary amide organic compound that contains an amide functional group at a terminal carbon atom (−CONH2) 

• Alcohols

• General formula

• Suffix

Alcohols are hydrocarbons that have a hydroxyl (−OH) functional group bonded to a carbon atom in the carbon chain 

• The hydroxyl group replace a hydrogen atom 

• Alcohols have a general formula C_nH_2n+1OH 

• Suffix is '-ol' 

The categorisation of an alcohol depends on - link this to primary, secondary and tertiary alcohols

The categorisation of an alcohol depends on the number of alkyl groups bonded to the carbon atom that the hydroxyl group is bonded to 

 

• In a primary alcohol, the carbon atom bonded to the hydroxyl group is bonded to only one alkyl group 

• In a secondary alcohol, the carbon atom bonded to the hydroxyl group is bonded to two alkyl groups 

• In a tertiary alcohol, the carbon atom bonded to the hydroxyl group is bonded to three alkyl groups 

T or F?

• Tertiary alcohols are very stable structures and consequently are unreactive.

• O-H bonds are not polar.

The answer is C 

 

Cannot be A as 

• No oxygen atom and no –OH (hydroxyl group) --> so not alcohol at all 

 

Cannot be B as 

• Contains a carboxyl (-COOH) --> so not alcohol at all 

 

It is C 

• As there is a hydroxyl group on the terminal carbon and hence an alcohol 

• The carbon atom bonded to the hydroxyl group is bonded to only one alkyl group 

Cannot be D 

• No oxygen atom and no –OH (hydroxyl group) --> so not alcohol at all 

• What do aldehydes and ketones have in common?

• T or F? C--O bonds are polar.

• Aldehyde

• T or F? It’s FG is never on the terminal carbon

• Draw diagram of FG

Aldehyde organic compound that contains a carbonyl functional group where one of the remaining bonds on the carbon atom in the carbonyl group is bonded to a hydrogen atom (−CHO)

-->  False. The carbonyl group is only on the terminal carbon 

• The remaining bond on the carbon atom in the carbonyl group can then bond with either a hydrogen atom or an alkyl group 

• Ketone

• T or F? It’s FG is never on the terminal carbon

• Draw diagram of FG

Ketone organic compound that contains a carbonyl functional group (C=O), where each of the two remaining bonds on the carbon in the carbonyl group are bonded to an alkyl group (-CO-) 

• Note that  the two alkyl groups bonded to the carbon in the CO group do not have to be the same 

• Ketone functional groups can only exist within the carbon chain (so never on the terminal carbon) 

Are you required to know this stuff about aldehydes and ketones:

• Naming them

• Structural/semi-structural/skeletal formulas

Not required to know naming these hydrocarbons rules, only structural, semi structural and skeletal formula

• Carboxylic acids

• Where is the FG always found?

• General formula

• What happens when it reacts with water?

• Suffix

An organic compound that contains a carboxyl functional group (−COOH) - which made up of two other functional groups: polar hydroxyl (−OH) and carbonyl (C = O) 

• The carboxyl group is always found at the end of the carbon chain 

• The carboxyl group may either bond to an alkyl group or a hydrogen atom 

• They have a general formula C_n-1H_2n-1 COOH or C_nH_2nO₂ ---> where you must count the C atom in the functional group –COOH 

 

• The highly electronegative O atoms draw electrons away from the H atom allowing it to form a H⁺ when it reacts with water.                                                             

• The name of the carboxylic acids ends in ‘oic acid' 

• esters

• Draw diagram of FG

• General formula

• What are esters used for usually?

Organic compounds that contain an ester functional group (−COO−) 

• This functional group is found within the carbon chain 

• One carbon atom in the ester group is linked to one oxygen atom through a double bond (a carbonyl) and to another oxygen atom through a single bond --> the oxygen atom is then itself bonded to an alkyl group 

• General formula R-COO-R^’ 

 

• The low molecular mass esters tend to have pleasant, sweet, fruity odours, found in many flowers and fruits 

• Esters are used as artificial flavourings, solvents, in paints and lacquers, perfumes and cosmetics 

T or F? In carboxylic acids and primary amides, the carbon atom in the carbonyl group is always the first carbon in the parent carbon atom chain. Why/why not?

T as these groups are always found at a terminal carbon

• Parent chain

• When functional groups are present, the direction of numbering is selected such that the numbers indicating the position of functional groups are as ___ as possible

The parent chain is the longest sequence of bonded atoms that include the relevant functional groups 

• e.g. all carboxyl groups must be part of the parent carbon chain. 

• It is usually the longest continuous sequence of carbon-carbon bonds in a molecule  

When functional groups are present, the direction of numbering is selected such that the numbers indicating the position of functional groups are as small as possible 

Does methene exist? Why/why not?

Methene doesn’t exist as double bonds between carbon atoms cannot occur with only one carbon atom present 

• Carbon branches are named by replacing the -ane ending with __

• Name this molecule

• Carbon branches are named by replacing the -ane ending with –yl

How are alkyl side chains named (hint: position)

Their position is indicated by a number before their corresponding prefix 

Name

Name

For these molecules, explain why the first one requires the number and the other doesn’t?

• When compounds have more than one side group bonded to parent chain --> alkyl groups prefixes are named in ___ order 

• Name this:

When compounds have more than one side group bonded to parent chain --> alkyl groups prefixes are named in alphabetical order 

  

• Molecule name: 4-ethyl-2-methyloctane ('e' goes before 'm') 

When multiple of the same functional group or side chain are present, a counting prefix is included

• Outline the FG prefix for these molecules

Name

T or F? Numbering the carbons in the carbon chain is now based on the location of the double bonds instead of the functional groups – the chain should be numbered to allow the double bond to occur at the lower numbered carbon 

True

Name

• The group with the ___ priority gets the lowest carbon number and maintains the suffix name 

• __ priority functional groups indicated by a prefix or alternate name

• List FGs from highest priority to lowest priority 

The suffix of the name of the compound is derived from the functional group with the highest priority 

• The group with the highest priority gets the lowest carbon number and maintains the suffix name 

• Lower priority functional groups indicated by a prefix or alternate name 

Note:

When writing the name of an organic compound, we need to ensure that we include the following conventions: 

• Commas are used to separate numbers representing positions of functional groups 

• Hyphens (-) are used to separate numbers from words.  

• There is no space between names of functional groups and the parent chain name. 

• Prefixes indicating functional groups need to be written in alphabetical order (not including prefixes such as di, tri, etc.) 

How to name esters:

• The alkyl group that originally comes from the alcohol and is attached to the oxygen atom by a single bond is named first 

--> where –anol becomes –yl 

 

• Which is then followed by the carbon chain that includes the carbon atom in the carbonyl of the ester bond and comes from the carboxylic acid 

--> where –oic becomes -oate 

Name:

This is called 'Propyl butanoate' 

• As the alkyl group that comes from the alcohol --> has 3 carbons --> 'prop' and this part has to end with 'yl' = 'propyl' 

• This is followed by the alkyl group that contains the carbon atom in the carbonyl --> 'butan' and this part has to end with '-oate' = 'butanoate' 

Structural isomers + show some for pentane

Structural isomers molecules with the same molecular formula but different spatial arrangement of atoms 

Example:

• They have the same molecular formula: C₅H₁₂ --> however, their structural formulas differ, resulting in them having different names 

•  Therefore, we can say that these three molecules are structural isomers of C₅H₁₂ 

 

There are some strategies that can be used to determine possible structural isomers of a molecule: 

• Changing the position of a functional group or side chain 

• Arranging available atoms into a branch/side chain 

• Changing the identity of the functional group 

TIP: Look at the number of carbons 

• 2,2,4-trimethylpentane has the molecular formula C₈H₁₆  

• Octane – has 8 carbons and hence 16 carbons 

• 3-ethylhexane --> 6 c (hexane) + 2 c (1 ethyl) = 8 c 

• 2,4-dimethylpentane --> 5 c (pentane) + 2 c ( 2 methyl) = 7 c --> thus C is the answer 

• 2,4-dimethylhexane --> 6 c (hexane) + 2 c (2 methyl) = 8 c 

Intermolecular Forces

Intermolecular Forces: Forces of attraction between molecules 

• Note not between atoms within a molecule – which is intramolecular bonds – its between molecules themselves 

• Dispersion forces

• Instantaneous dipole

• T or F? All organic compounds experience dispersion forces between their molecules 

• Which homologous series only experience dispersion forces

Dispersion forces : Weak intermolecular forces caused by the electrostatic attraction between instantaneous dipoles in adjacent molecules 

• Instantaneous dipole is a partial positive and negative charge that suddenly appears in an atom or molecule due to the random movement of electrons 

• True. All organic compounds experience dispersion forces between their molecules 

• Alkanes and alkenes only experience dispersion forces between molecules 

What factors increase dispersion forces:

• Permanent dipole-dipole attraction + in order for a molecule to be polar, what does it require

• Permanent dipole

• What factor influences permanent dipole-dipole attractions

• What homologous series experience permanent dipole-dipole attractions?

The strength of a permanent dipole-dipole attraction depends on the difference in electronegativity of the atoms involved in the relevant polar bonds – where greater difference means stronger dipole-dipole attraction 

 

The following organic compounds experience permanent dipole-dipole attraction in addition to dispersion forces: 

• Aldehydes (polar C=O bond) 

• Ketones (polar C=O bond)  

• Esters (polar C=O bond)  

• Haloalkanes (polar C−X bond, where X represents a halogen) 

• Hydrogen bonding

• In this type of bonding, which atom has a partial + charge and which atom has the partial - charge

A type of permanent dipole-dipole attraction that only occurs between molecules in which hydrogen is bonded directly to either nitrogen, oxygen, or fluorine (NOF) 

• In all instances of hydrogen bonding, the hydrogen atom has a partial positive charge and is attracted to a nitrogen, oxygen, or fluorine atom with a partial negative charge on an adjacent molecule 

• A common occurrence of hydrogen bonding is between water molecules 

What homologous series experience hydrogen bonding in addition to dispersion forces:

• Alcohols (highly polar O−H bond)  

• Carboxylic acids (highly polar O−H bond) (also experience dipole-dipole interactions due to C=O bond)  

• Primary amines (highly polar N−H bonds)  

• Primary amides (highly polar N−H bonds) (also experience dipole-dipole interactions due to C=O bond) 

• Boiling point

• Melting point

• The stronger the electrostatic attraction between molecules, the more __ required to overcome them 

The boiling point of a liquid is defined as the temperature at which it changes from its liquid state to a gaseous state 

 

The melting point of a solid is the temperature at which it transitions from a solid to a liquid state 

 

• The stronger the electrostatic attraction between molecules, the more energy (often heat, or thermal energy) required to overcome them 

• Viscosity + give examples

• Link viscosity with the strength of intermolecular forces

• Explain a factor that affects viscosity

Viscosity measures a substance’s resistance to flow and reflects the substance’s structural properties 

• Liquids with high viscosity, like honey, flow very slowly 

• Whilst those with low viscosities, like water, flow more readily 

 

• Liquids with stronger intermolecular forces have stronger attractive forces holding the molecules together, making it harder for the substance to flow 

• While non-polar substances that mainly experience dispersion forces, like cooking oil, tend to be less viscous because their intermolecular forces are weaker, allowing them to flow more readily in comparison 

 

As viscosity is dependent on the intermolecular reactions between molecules, changes in temperature (and hence thermal energy) can affect the ability of substances to flow 

• For example, an increase in temperature results in a decrease in viscosity as there is more energy available to overcome these forces, allowing substances to flow more readily 

• Conversely, a decrease in temperature results in an increase in viscosity 

As melting and boiling points increase, so does viscosity. Explain why.

Answer is D 

This is because: 

• The first molecule (in the order) will be the one which is the most able to flow – less viscous --> meaning that they have weaker intermolecular forces 

• While the last molecule will be the one least able to flow – more viscous --> meaning that they have stronger intermolecular forces 

 

• Compound 2 is the most polar due to its three highly polar (O−H) bonds and would experience hydrogen bonding between its molecules 

• Compound 3 is the next most polar due to its singular (O−H) bond and would also experience (slightly less) hydrogen bonding between molecules 

• Compound 1 only experiences weak dispersion forces between its molecules 

--> Thus the order from least viscous to most viscous is D 

Draw a summary table for each of these:

• Alkanes

• Alkenes

• Haloalkanes

• Alcohols

• Carboxylic acids

• Ester

• Amines

• Aldehydes

• Ketones

• Primary amides

And include these (note that not all of these would be filled out for each series)

• FG + symbol

• Prefix/suffix

Are alkanes and haloalkanes:

• Saturated

• Polar

• Insoluble in water

• Alkanes are saturated, non-polar and insoluble in water.  

• Haloalkanes are saturated, polar and soluble in water 

Substitution reaction

Substitution reaction chemical reaction where an atom, or group of atoms, is replaced by another atom, or group of atoms resulting in the formation of a new substance 

Substitution reaction between alkanes and halogens 

Complete this reaction: ethane + Bromine (Br-Br)

Substitution reaction between primary haloalkanes and an alkali (base soluble in water) 

Complete this reaction: bromoethane + sodium hydroxide

 

• Substitution reaction between primary haloalkanes and water 

• T or F? This reaction is very fast

Complete this reaction:

Bromoethane + water