AP/IB REVIEW PACKET:

ORGANIC CHEMISTRY

Conceptual & Mathematical Models to Review

Homologous Series…

  1. Hydrocarbons are a series of organic molecules that are made of only hydrogen and carbon
  2. The simplest series of organic compounds are the alkanes

a. All carbon atoms are singly bonded, therefore saturated

b. The alkanes make up a homologous series

  1. A set of compounds that differ by a CH2 group
  2. Homologous series have similar chemical properties by varying physical properties.
  3. For example, the alkanes are relatively inert (chemical property)
  4. Have low boiling points that increase within the series because of
  5. Higher mass and
  6. Increased dispersion forces due to larger molecules/more electrons

Alkane Homologous Series example:

Alcohols Homologous Series example:

Organic Naming and Formulas:

  1. Organic structures are named through a system of prefixes and suffixes.
  2. Prefix = number of carbon atoms
  3. Suffix = functional group.
  4. – ane = saturated carbon chain made only of C and H
  5. Table of prefixes and names for the simple alkane, alkene, and alcohol homologous series

# C / Prefix / Alkanes -ane / Alkenes - ene / Alcohols - anol
1 / Meth- / Methane / Methene / Methanol
2 / Eth- / Ethane / Ethene / Ethanol
3 / Prop- / Propane / Propene / Propanol
4 / But- / Butane / Butene / Butanol
5 / Pent- / Pentane / Pentene / Pentanol
6 / Hex- / Hexane / Hexene / Hexanol

butane 2-methyl propane

(isobutane)

Other formula/name examples:

Structural Isomers & Substituent Groups
  1. Sometimes one molecular formula can describe more than one molecule, in which the same atoms are bonded together in different arrangements (think about the different ways you put the legos together)
  2. Such molecules are known as structural isomers of each other:
  3. Structural isomers: molecules possessing the same molecular formula but different arrangement of atoms and therefore different structural formulas.
  4. These isomers are distinct in their physical and chemical properties.
  5. Example: see isomers of butane above.

Organic formulas

1.C2H5 – empirical formula, gives only the ratio of elements

  1. C4H10 – molecular formula, gives only the number of atoms in the molecule
  2. CH3CH2CH2CH3 – a kind of structural formula

Properties of functional groups  See handout

Functional Groups to pay most attention to:

-Alkanes, Alkenes

-Alcohols

-Aldehydes & Ketones

-Carboxylic acids

-Halides

IB: be able to identify these functional groups in structural formulas:

-Amino (NH2)

-Benzene ring

-Esters

Reactions summary  See handout

Reactions to be familiar with:

-Combustion (all hydrocarbons and functional groups, know complete and incomplete)

-Substitution reactions (elements substitute for hydrogen - alkanes)

-Addition reactions (across a double bond - alkenes)

-Polymerization (of alkenes)

-Oxidation (of alcohols to aldehydes/ketones)

IB Examples:

1.(i)Ethanoic acid reacts with ethanol in the presence of concentrated sulfuric acid and heat. Identify the type of reaction that takes place. Write an equation for the reaction, name the organic product formed and draw its structure.

(4)

(ii)State and explain the role of sulfuric acid in this reaction.

(2)

(iii)State one major commercial use of the organic product from this type of reaction.

(1)

(Total 7 marks)

2.For the two compounds HCOOCH2CH3 and HCOOCHCH2:

III

(i)State and explain which of the two compounds can react readily with bromine.

(2)

(ii)Compound II can form polymers. State the type of polymerization compound II undergoes, and draw the structure of the repeating unit of the polymer.

(2)

3.The alkanes are a homologous series of saturated hydrocarbons.

(a) state the meaning of each of the following terms.

(i)homologous series(2)

(ii)hydrocarbon(1)

(iii)saturated(1)

(b) (i)State and explain the trend in the boiling points of the first five alkanes.(2)

(ii)Explain why the enthalpies of combustion of alkanes are negative values.(1)

(c) State the products of the complete combustion of alkanes.(2)

(Total 9 marks)

4.The percentage composition of a hydrocarbon is 85.6% carbon, 14.4 % H.

(a)Calculate the empirical formula of the hydrocarbon.(2)

(b)A 100 g sample of the hydrocarbon at a temperature of 273 K and a pressure of 1.01 x 105 Pa (1.00 atm) has a volume of 0.399 dm3.

(i)Calculate the molar mass of the hydrocarbon.(2)

(ii)Deduce the molecular formula of the hydrocarbon.(1)

(c)Explain why the incomplete combustion of hydrocarbons is harmful to humans. (2)

(Total 7 marks)

5.Ethene, propene, and but-2-ene are members of the alkene homologous series.

(a)Describe three features of members of a homologous series.(3)

(b)State and explain which compound has the highest boiling point.(3)

(c)Draw the structural formula and give the name of an alkene containing five carbon atoms. (2)

(d)Write an equation for the reaction between but-2-ene and hydrogen bromide, showing the structure of the organic product. State the type of reaction occurring. (3)

(e)Propene can be converted to propanoic acid in three steps:

Step 1 Step 2 Step 3

Propene Propan-1-ol PropanalPropanoic acid

State the type of reaction occurring in steps 2 and 3 and the reagents needed. Describe how the conditions of the reaction can be altered to obtain the maximum amount of propanal, and in a separate experiment, to obtain the maximum amount of propanoic acid. (5)

(f)Identify the strongest type of intermolecular force present in each of the compounds propan-1-ol, propanal, and propanoic acid. List these compounds in decreasing order of boiling point. (4)

(Total 20 marks)

6. Give the structural formula for the isomers of molecular formula C5H12 and state the name of each one. (Total 6 marks)

7.(a)Describe three features of members of a homologous series.(3)

(b)Ethanol and ethanoic acid can be distinguished by their melting points. State and explain which of the two compounds will have a higher melting point. (2)

(Total 5 marks)

AP Examples:

See 2003 #8 from Bonding / IMF’s packet.

See 2005 #2 from Colligative Properties packet.

2003 #6 – part c

6.For each of the following, use appropriate chemical principles to explain the observation. Include chemical equations as appropriate.

a.In areas affected by acid rain, statues and structure made of limestone (calcium carbonate) often show signs of considerable deterioration.

b.When table salt (NaCl) and sugar (C12H22O11) are dissolved in water, it is observed that

i.both solutions have higher boiling points than pure water, and

ii.the boiling point of 0.10 M NaCl (aq) is higher than that of 0.10 M C12H22O11 (aq).

c.Methane gas does not behave as an ideal gas at low temperatures and high pressures.

d.Water droplets form on the outside of a beaker containing an ice bath.

1995 #2

2) Propane, C3H8, is a hydrocarbon that is commonly used as fuel for cooking.

(a) Write a balanced equation for the complete combustion of propane gas, which yields CO2(g) and H2O(l)

(b) Calculate the volume of air at 30°C and 1.00 atmosphere that is needed to burn completely 10.0 grams of propane. Assume that air is 21.0 percent O2 by volume.

(c) The heat of combustion of propane is -2,220.1 kJ/mol. Calculate the heat of formation, H°f, of propane given that H°f of H2O(l) = -285.3 kJ/mol and H°f of CO2(g) = -393.5 kJ/mol.

(d) Assuming that all of the heat evolved in burning 30.0 grams of propane is transferred to 8.00 kilograms of water (specific heat = 4.18 J/g · K), calculate the increase in temperature of the water.

2001 #8, part b

8.Account for each of the following observations about pairs of substances. In your answers, use appropriate principles of chemical bonding and/or intermolecular forces. In each part, your answer must include references to both substances.

a)Even though NH3 and CH4 have similar molecular masses, NH3 has a much higher normal boiling point (-33 oC) than CH4 (-164 oC).

b)At 25 oC and 1.0 atm, ethane (C2H6) is a gas and hexane (C6H14) is a liquid.

c)Si melts at a much higher temperature (1,410 oC) than Cl2 (-101 oC).

d)MgO melts at a much higher temperature (2,852 oC) than NaF (993 oC).

2006 #6 a-c

6.Answer each of the following in terms of principles of molecular behavior and chemical concepts.

(a) The structures for glucose, C6H12O6, and cyclohexane, C6H14, are shown below.

Identify the type(s) of intermolecular attractive forces in

(i) pure glucose

(ii) pure cyclohexane

(b)Glucose is soluble in water but cyclohexane is not soluble in water. Explain.

(c)Consider the two processes represented below.

Process 1:H2O(l)  H2O(g)H = +44.0 kJ mol1
Process 2:H2O(l)  H2(g) + H = +286kJ mol1

(i) For each of the two processes, identify the type(s) of intermolecular or intramolecular attractive forces that must be overcome for the process to occur.

(ii) Indicate whether you agree or disagree with the statement in the box below. Support your answer with a short explanation.

2002 #3

3.Consider the hydrocarbon pentane, C5H12 (molar mass 72.15 g).

a.)Write the balanced equation for the combustion of pentane to yield carbon dioxide and water.

b.)What volume of dry carbon dioxide, measured at 25 oC and 785 mm Hg, will result from the complete combustion of 2.50 g of pentane?

c.)The complete combustion of 5.00 g of pentane releases 243 kJ of heat. On the basis of this information, calculate the value of H for the complete combustion of one mole of pentane.

d.)Under identical conditions, a sample of an unknown gas effuses into a vacuum at twice the rate that a sample of pentane effuses. Calculate the molar mass of unknown gas.

e.)The structural formula of one isomer of pentane is shown below. Draw the structural formulas for the other two isomers of pentane. Be sure to include all atoms of hydrogen and carbon in your structures.

2004 #8

8.

The gas-phase conversion reaction between the geometric isomers cis-2-butene and trans-2-butene is represented by the equation above. The value of the equilibrium constant, Keq, for the reaction is 3.2 at 298 K and 1.0 atm.

a)In a mixture of the isomers at equilibrium at 298 K and 1.0 atm, which is present at a higher concentration, cis-2-butene or trans-2-butene? Justify your answer.

b)If 1.00 mol of pure cis-2-butene and 1.0 mol of pure trans-2-butene were introduced into an evacuated container at 298 K, in which direction (to the right or to the left) would the reaction proceed to establish equilibrium? Justify your answer.

c)Given that Keq for the reaction at 400 K has the value 1.3, predict whether the reaction is endothermic or exothermic. Justify your answer.

d)There are other structural isomers of cis-2-butene and trans-2-butene. Draw one of these isomers, including all atoms, and give its IUPAC name.

Various Examples from past AP Questions #4

(a)Methane gas is mixed with an excess of chlorine gas.

(b)Solutions of potassium hydroxide and propanoic acid are mixed.

(c)Propanone is burned in air.

(d)Propene is burned in air.

(e)Propanal is burned in air.

(f)Butanol is burned in air.

(g)Solid dinitrogen pentoxide is added to water.

(h)Hexane is combusted in air.