Functional Groups: Classification of Organic Compounds (SL IB Chemistry)

Organic compounds are classified into families called a homologous series.

State three features of members belonging to the same homologous series.

Table 1 shows the boiling points of the first five members of the alkane family.

 Table 1

On the axes below in Figure 1, draw a graph of boiling point against the number of carbon atoms in the alkanes. Estimate the boiling point of the next member of the homologous series, hexane, C₆H₁₄, and show on your graph how you arrived at your estimated boiling point. 

Figure 1

Estimated boiling point of hexane : ________ ^oC

State the general formula for an alkyne and give the molecular formula and name of the fifth member of the alkyne family.

The boiling point of ethyne, C₂H₂, is -84 ^oC.

State with, with a reason, whether the boiling point of ethyne would be expected to be higher or lower than the boiling point of ethane, C₂H₆.

Geraniol is a colourless component of rose oil whose structure is shown in Figure 1.

 Figure 1

Butan-2-ol is an organic compound used industrially to make butanone.

Draw and name all the branched-chain isomers of butan-2-ol.

State, with a reason, the class of alcohols which butan-2-ol belongs to.

The formulae of four organic compounds are given in Table 1. Write the names of the compounds in the second column.

Table 1

Which of the compounds in part (a) are structural isomers of each other and what type of isomerism do they show?

Propofol is a drug used to reduce consciousness during medical procedures. The skeletal structure of propofol is given in Figure 1.

Figure 1

Valeric acid, C₅H₁₀O₂, is a straight chain carboxylic acid found in the plant Valeriana officinalis.

Draw and name all the possible isomers of C₆H₁₄.

Figure 1 below shows a three-dimensional structure of a molecule.                                                  

Figure 1 

Toluene is a common organic chemical with many industrial and commercial applications. Toluene is also known as methylbenzene. 

Draw the molecular structure of toluene.  

Another derivative of benzene has the molecular formula C₈H₁₀. 

Draw the structures of the four possible isomers of this derivative.

The analytical instruments used for identification of organic compounds are constantly being improved.            

 Mass spectroscopy is one such analytical tool which provides key information used to identify an unknown compound. 

An unknown compound has the empirical formula C₂H₄O, and its mass spectrum has a molecular ion peak at m/z 84.

Deduce the molecular formula of the compound.  

The unknown compound is a carboxylic acid. Deduce the two possible carboxylic acid structural isomers.  

A group of students are asked to distinguish between four samples of different organic compounds.            

The four samples are as follows: 

• A primary alcohol 
• A tertiary alcohol 
• An aldehyde 
• A carboxylic acid

Describe how the group of students could distinguish between the two different alcohols.

A molecule of oleic acid is shown.

Oleic acid is a fatty acid which occurs naturally in different animals and plants.

Oleic acid exhibits stereoisomerism. Explain the meaning of this term and identify why oleic acid has stereoisomers.

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

A chemist is analysing a collection of organic compounds. The structural formulae of these compounds are shown.

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

This question refers to the compounds in the table in part (a)

2-methylbut-2-ene can be converted into 2-methylbutan-2-ol, a liquid that smells of camphor. 

State the reagents needed to convert 2-methylbut-2-ene into 2-methylbutan-2-ol.

Dichloroethene exists as two stereoisomers. Draw the structures of these isomers. 

Explain why dichloroethene has stereoisomers.

State the IUPAC names for the isomers of C₅H₁₂O that are primary alcohols.

State the IUPAC name for the following primary alcohols.

Draw the displayed formula for a straight chain isomer of CH₂(Br)CH(CH₃)CH₂OH.

The empirical formula of the compound in part b) i). 

Phenacetin is a pain killer though the use of this was banned as it was found to cause harm to kidney function.

Deduce the molecular formula of phenacetin. 

Identify the names of the three functional groups present in phenacetin.

Aspirin is a common pain killer and has the following structure.

State the empirical formula of aspirin.

Aspirin is formed from ethanoic anhydride and compound A. State the IUPAC name of compound A.

Clenbuterol, shown below, is considered a performance enhancing drug and is believed to increase short term work rate and cardiovascular output.

Deduce the functional groups marked x and y and state to which class they belong to.

Lactic acid has the molecular formula of C₃H₆O₃, and the structural formula of CH₃CHOHCOOH.

Illustrate the types of isomerism shown by C₃H₆O₃.