Basic Concepts (OCR A Level Chemistry)

Oleic acid, shown below, is a fatty acid which occurs naturally in different animals and plants. It is also widely produced in industry, for its uses as an emulsifying agent and in the pharmaceutical industry.

The structure of another fatty acid commonly found in milk is shown.

Name the fatty acid.

Crotonic acid is another fatty acid which has a similar structure to oleic acid. The molecular formula of crotonic acid is C₄H₆O₂.

Two students, Student A and Student B, discuss the properties of oleic acid and crotonic acid. 

Student A claims that both compounds belong to the same homologous series and Student B claims that both compounds have similar chemical properties.

Are either of the students correct? Explain your answer.

Crude oil consists of a mixture of hydrocarbons, which can be separated by fractional distillation.

The shorter hydrocarbons are more useful as fuels such as gasoline and diesel fuel, so longer hydrocarbons are often converted into shorter ones in a process called cracking.

Cracking of hydrocarbons results in the formation of shorter alkanes and alkenes.

A hydrocarbon with molecular formula C₁₂H₂₄ is cracked to form oct-1-ene and one other alkene.

The reaction mechanism for the reaction of but-1-ene with hydrogen bromide forming compound X is shown below, with errors:

Give the IUPAC name of compound X.

Compound X can also be formed from the reaction of butane with bromine using ultraviolet light.

CH₃CH₂CH₂CH₃ + Br₂ → CH₃CH₂CHBrCH₃ + HBr

The mechanism for this reaction occurs in three steps:

1. Initiation
2. Propagation
3. Termination

State what type of reaction this is and the type of bond fission involved.

A chemist is analysing a collection of organic compounds. The formulae of these compounds are shown in the table below:

Compound	Formula	IUPAC name
1	CH3CHCClCH2OH
2
3
4

 Give the IUPAC name for the compounds to complete the table.

Draw the skeletal formula for a straight chain isomer of compound 2.

State the empirical formula of compound 1, CH₃CHCClCH₂OH.

Compounds 1 and 4 can react in a similar fashion with some chemicals, while other chemicals can be used to distinguish between them.

Pentane belongs to the homologous series of alkanes.

The compound 2,2-dimethylpropane can be represented using different types of formula.

Its structural formula can be shown as (CH₃)₄C.

Pent-1-ene (C₅H₁₀) is a member of the homologous series of alkenes. 

Pent-1-ene (C₅H₁₀) has structural isomers but no stereoisomers.

This question is about the structure of organic compounds.

The structure of an alcohol X is shown below.

2,3-dimethylpentan-1-ol is distilled with acidified potassium dichromate(VI) solution. During this distillation, 2,3-dimethylpentan-1-ol is oxidised to an aldehyde. 

1-Bromopropane reacts with aqueous sodium hydroxide according to the following reaction mechanism.

1-Bromobutane can also react via a free-radical substitution mechanism as shown. 

Explain how the butyl and bromine radicals are formed.

This question is about organic compounds

Terpenes are a class of organic compounds widely used as fragrances in products such as perfumes. For example, one of the simpler terpenes, nerol is found in many essential oils such as lemongrass and hops. The structure of nerol is shown in Figure 1 below.

Figure 2 shows the skeletal formula of a type of fuel.  

Figure 2

A compound with a molar mass of 72.0 g mol^-1 is composed of 66.63% C, 11.18% H, and 22.19% O. 

This question is about Ethers.

Ethers are a homologous series of organic compounds containing the R−O−R functional group.

The structures and names of two ethers are shown in Figure 1.

Figure 1

Ethers can be prepared by nucleophilic substitution of haloalkanes with alkoxide ions, RO⁻. 

Alkoxide ions can be prepared by reacting sodium with an alcohol. A gas is also formed.

Write an equation for the formation of methoxide ions from sodium and an alcohol.

Methoxyethane, shown in part (a), can be prepared by reacting bromoethane, CH₃CH₂Br, with methoxide ions, CH₃O⁻.

Outline the mechanism for the nucleophilic substitution of CH₃CH₂Br with CH₃O⁻ using skeletal formulae.

Your answer should include relevant charges, dipoles and the products formed.

In this mechanism, CH₃O⁻ ions have acted as a nucleophile.

[1]

This question is about saturated hydrocarbons.

Compound A is shown in Figure 1.

Figure 1

The reaction of compound A with excess fluorine forms compound D, which has a molar mass of 140 g mol⁻¹.

Draw a possible structure for compound D and write the equation for its formation from compound A. Use molecular formulae in the equation.

The hydrocarbon propane can be reacted with chlorine to prepare 2-chloropropane, CH₃CHClCH₃, by free radical substitution.

Oxybenzone is a UV light-absorbing chemical which is found in certain sun creams. The structure of oxybenzone is shown in Figure 2 below.

Oxybenzone contains an ether functional group, C-O-C. Identify the other functional groups present in oxybenzone.

One of the starting molecules used in the synthesis of oxybenzone is shown in Figure 3 below.

Draw the skeletal formula of two other structural isomers of this molecule.

This question is about molecules containing hydroxyl groups.

A student named the alcohol molecule shown in Figure 1 as E-1,3-dichlorohex-2-ene-6-ol.

Figure 1

State the errors the student has made in naming the molecule and give the correct IUPAC name.

Aspirin is an ester of salicylic acid, HOC₆H₄CO₂. Aspirin is formed when an ester bond is created between the salicylic acids OH group and ethanoic anhydride, (CH₃CO)₂O, in the presence of an acid catalyst, as shown in Figure 2. Ethanoic acid is also formed as a product.

Figure 2

The organic compounds in Figure 3 below can be termed aliphatic, alicyclic or aromatic.

Figure 3

Each response may contain more than one letter for the questions below.

This question is about organic compounds found in living organisms.

Two structural isomers of C₁₀H₁₈O are linalool and geraniol. They are unsaturated alcohols with similar chemical properties and are both used in perfumes. 

The IUPAC names for both linalool and geraniol are shown in Table 1.

Table 1

Draw the skeletal formulae for these two isomeric alcohols.

The organic compounds below in Figure 2 are all made by living organisms.

Figure 2

5.175 g of compound D (from part C) is reacted with an excess of hydrogen chloride. The mixture of products contains 90% by mass of one product and 10% by mass of the other product.

Calculate the mass of each product formed.