Chemistry: Topic 7 – Organic Chemistry

Terms in this set (45)

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– A compound made up of hydrogen and Carbon’s atom, only.

– A simple hydrocarbon.
– They have the general formula: C n H 2 n+2
– The alkanes are a homologous series, which are a group of organic compounds that react in a similar way.
– They are saturated compounds, meaning each carbon atom forms 4 single covalent bonds.
– The first 4 Alkanes are: Methane, Ethane, Propane and Butane

How do you draw a displayed formula for an alkane?

What are the properties of short chain alkanes?

– Not/less viscous (gloopy)
– More volatile (e.g. lower boiling point)
– Shorter chains are usually more flammable as well.

What is complete combustion of a hydrocarbon?

– When there is oxygen, hydrocarbons can go through, complete combustion.
– This releases a lot of energy.
Hydrocarbon + oxygen –> carbon dioxide + water (+ energy)
– During combustion, both carbon and hydrogen are oxidised.
– Hydrocarbons are used as fuels due to the amount of energy released when they combust completely.

Fractional distillation

…

Uses and Cracking of crude oil

…

What are alkenes?

– Alkenes are hydrocarbons which have a double bond between two of the carbon atoms in their chain.
– The C=C double bond means the alkane will have fewer hydrogen’s compared to alkanes. This makes Alkenes unsaturated.
– The C=C double bond can open up to form a single bond, allowing the two carbon atoms to bond with other atoms. This make Alkenes more reactive (compared to alkanes)
– The first 4 alkenes are: Ethene, Propene, Butene and Pentene
– The General formula for Alkenes is: C n H 2n

Why do alkenes burn with a smoky flame?

– In large amounts of oxygen, Alkenes completely combust, producing only water and carbon dioxide.

– However, if there isn’t enough Oxygen, they undergo incomplete combustion. This still produces carbon dioxide and water, but i can also produce carbon and carbon monoxide which, are both, poisonous. The formula for this, is as follows:

Alkene + oxygen –> Carbon + Carbon dioxide + Carbon monoxide + water (+ Energy)

– Incomplete combustion results in a smoky yellow flame and less energy being released.

What is addition reactions with Alkenes?

– Alkenes have the functional group C=C meaning they all react in similar ways.
– Most of the time alkenes react via addition reactions. The carbon-carbon double bond will open up to leave a single bond and a new atom is added to each carbon.

What is addition reactions with hydrogen?

– Also known as hydrogenation, hydrogen can react with the double bonded carbons to open up the double bond and for the equivalent, saturated alkane.
– The alkene is reacted with hydrogen in the presence of a catalyst

What happens when alkenes react with steam?

– When alkenes react with steam, water is added across the double bond and an alcohol is formed.
– e.g. ethanol can be made by mixing ethene with steam and then passing it over a catalyst

What is the alcohol functional group?

OH-

Name some uses of Alcohols

– Fuels
– Solvents
– Beverages

What does homologous mean (in terms of Alcohols)?

– They all have the same functional group. In this case all Alcohols have a OH-

What is the Structural formula of Methanol?

– CH 3 OH

What is the displayed formula for Methanol?

H
|
H – C – OH
|
H

What is the purpose of hydrating ethene?

– To make ethanol

What are the Pro’s and Con’s of Hydrating ethanol?

– One Pro is that the reaction produces a high yield of ethanol.
– However, the reaction requires a lot of energy as it needs to be a high temperature. Also ethene comes from crude oil, which is non-renewable.

What is the purpose of fermenting sugar?

– To make ethanol (alcohol)

What is the word equation for fermentation of sugar?

Glucose (+yeast) –> ethanol + Carbon dioxide

Describe the method of Fermenting sugar…

Firstly, sugar is heated to 37°C, with the addition of yeast. The conditions must also be anaerobic (without alcohol). Which, as a result, produces ethanol and carbon dioxide.

Methanol is used to produce methanoic acid.
What type of substance reacts with Methanol to produce methanoic acid?

An oxidising agent

Name the gas produced when sodium is added to ethanol

Hydrogen gas

What are some uses of esters

– Food flavouring
– Fragrances
– Industrial solvents

What is the equation for the formation of an Ester?

Alcohol + Carboxylic acid –> Ester + water

What carboxylic acid is found in vinegar?

Ethanoic acid

Ethyl propanoate is made by reacting ethanol with propanoic acid. What type of organic compound is ethyl propanoate?

Ester

Solutions of ethanoic acid and hydrochloric acid with the same concentration have different pH values.
Explain why the solution of ethanoic acid has a higher pH than the solution of hydrochloric acid.

Because aqueous solutions have different pH values for different Concentrations, and ethanoic acid is weak.

What does volatile mean?

How easily a substance evaporates at room temperature.

What is addition polymerisation?

– All monomers are the same (only one type)
– Contains a C=C monomer
– The monomers with carbon-carbon double bonds react together to form a long chain polymer.
– only one product is produced

What is condensation polymerisation?

– When 2 different monomers with different functional groups react.
– It produces 2 products and one small water molecule
– The 2 reactive functional groups react in the monomer

What are some examples of a natural polymer?

– Proteins are polymers of amino acids
– Starch and cellulose are sugar polymers (glucose and fructose)
– Starch, Sugars and Cellulose are Carbohydrates

What is the equation for Glucose monomers when they go through condensation polymerisation?

Glucose monomers –> Starch polymers (+H2O)
Glucose monomers –> Cellulose polymers (+H2O)

What is the equation for Amino acid monomers when they go through condensation polymerisation?

Amino acid monomers –> protein polymers (+H2O)

What is the functional group of amino acids?

– Amino acids have 2 functional groups: a basic amino acid group (NH2) and an acidic carboxylic acid group (COOH)
– Amino acids can be combined by condensation polymerisation to produce polypeptide

What is the displayed formula for an amino acid?

– NH2 functional group

– COOH functional group (Carboxylic acids)

Image: What is the displayed formula for an amino acid?

What is the functional group for Carboxylic acids?

-COOH

Describe a DNA molecule

– made from Nucleotide polymers
– A large molecule essential for life. It codes for genetic instruction
– It has 2 polymer chains
– Made from 4 different polymers called nucleotides (A, T, G, C)
– Its in the shape/form of a double helix

Name 2 reactions of Carboxylic acids

– A Carboxylic acid reacted with a metal carbonate forms salt, CO2 and water.
e.g. Sodium carbonate + Ethanoic acid -> Sodium Ethanoate + water

– A Carboxylic acid reacts with alcohols (in the presence of a catalyst, Concentrated H2SO4) to for an Ester and Water.
e.g. Ethanoic acid + Ethanol –> Ethyl Ethanoate + Water

Properties of carboxylic acids

– dissolve in water, if it contains up to 5 Carbon atoms. With more then 5 C- atoms it becomes less soluble
– form solutions with pH value of around 3-7
– when added to carbonates, they fizz/bubble (CO2 produced)
– react with acids to produce esters (in the presence of an acid catalyst).
– As its a weak acid, it only partially ionises releasing some H+ ions in an aqueous solution.

Name 2 reactions that produce Ethanol

– Ethene + steam
– Fermentation

What are advantages and disadvantages of producing Ethanol by the Ethene + steam method?

Advantages

– Its a fast process

– Produces 100% ethanol

Disadvantages

– Uses crude oil which are fossil fuels (non- renewable)

What are advantages and disadvantages of producing Ethanol by Fermentation?

Advantages

– Uses plants (renewable), and carbon neutral (photosynthesis etc)

Disadvantages