Download CHEM120 - ORGANIC CHEMISTRY WORKSHEET 1

CHEM120 - ORGANIC CHEMISTRY WORKSHEET 1
Some of the objectives

To understand and know the hybridization concept

Be able to distinguish different geometries, including basic bond lengths
and angles within organic structures

Name organic molecules

Be able to identify different functional groups and name them.

Know how to draw organic structures given the name or vice-versa, i.e.
given the structure you should be able to name the compound

Be able to use line notation and the condensed form to draw your
structures as well as being able to draw the complete structure with all the
atoms shown.

You should be able to draw and name different kind of alcohols or amines,
i.e. primary (1˚), secondary (2˚), tertiary (3˚) and quaternary (in the case
of amines).
Problems
1. Answer the following questions with respect to compounds (A) and (B):
5
CH(CH3)2
(A) CH3C
1
2
CCH
CHCH2
4
(B) 6
CHCH2CHCH2COOC(CH3)3
2
O
3
OCHCH3
CH3CH(OH)CH 2CCH
3
1
CH2
CH2CH3
(a) Draw the bond-line notation for the two compounds.
(b) Identify the following substituents on structure 1(A):
(i)
an isopropyl group
1 Dr. V.O. Nyamori
(First Year Chemistry Co-ordinator) (ii)
a tert-butyl group
(iii) a sec butyl group
(c) Identify all the functional groups in compounds (A) and (B).
(d) Identify the hybridization of the numbered atoms in structures (A) and
(B).
2. Name the compounds (a) to (d) below according to the IUPAC rules.
(a) CH3CH2CH(CH3)CH2CH(CH2CH3)CH3
(b)
(c)
(d)
3. Write (i) structural formulae and (ii) draw the bond line notation for the
following compounds:
(a) 2,2,4-trimethylhexane
(b) 3-ethyl-2,4,5-trimethyloctane
(c) 2-bromo-2,4,6-trimethyloctane
4. (a) Explain why 2-sec-butyloctane is an incorrect IUPAC name.
(b) (i) Write a correct IUPAC name and (ii) draw the bond-line notation for
the intended compound.
(c) Identify a primary (1˚), secondary (2˚), tertiary (3˚) and a quaternary
(4˚) carbon atom in CH3C(CH3)2CH2CH(CH3)CH3.
2 Dr. V.O. Nyamori
(First Year Chemistry Co-ordinator) CHEM 120: ORGANIC CHEMISTRY: WORKSHEET 2
Some of the objectives

Be able to identify and name different isomers by using acceptable organic
nomenclature rules, i.e. for constitutional, geometric and optical isomers.

Be able to draw by using a perspective formula, Newman projections and
Fischer projections.
Problems
1. Name the following compounds by using the IUPAC system. If any alcohols
are present, indicate whether they are primary, secondary or tertiary.
2. Draw structures for:
(a) 4-isopropyldecane
(b) 2,2-dichloropropane
3 Dr. V.O. Nyamori
(First Year Chemistry Co-ordinator) (c) 3-heptyne
(d) 5,5-dimethylnonane
(e) 2-butanol
(f) 2-methyl-2-propanol
(g) 3-methylpentanal
(h) 3-hydroxy-2-hexanone
(i) octanoic acid
(j) 4-bromo-5 hydroxynonanoic acid
3. There are four structural isomers with the molecular formula C4H9Br.
Draw
structures for the four isomers. One of these can exist as a pair of optical
isomers which one is this?
4. The substance 2-butanol displays optical isomerism.
carbon with a ‘*’.
Indicate the chiral
Draw three dimensional representations of the two
enantiomers and label the isomers clearly.
5. Draw structures for the cis- and trans-isomers of 1-chloro-1-propene.
6. Determine the configuration of each of the following alkenes:
7. Draw
the structure of trans-
1,3-
dichlorocyclobutane.
4 Dr. V.O. Nyamori
(First Year Chemistry Co-ordinator) 8. Explain why the cyclohexane boat conformation is much less stable than the
chair conformation.
9. Find the stereogenic center (chiral centre) in
i) CH3CH2CHICH2CH3
ii) BrFCHCH3
iii) 3-methylcyclohexene
iv) 2,3-dibromobutane
10. (a) Which of the following compounds is chiral?
i) 1-bromo-1-phenylethane
ii) 1-bromo-2-phenylethane
(b) Draw three-dimensional structures (perspective formulae) for the two
enantiomers of the chiral compound in problem 10(a).
11. The figure below shows Fischer projection structures of 2,3-dichlorobutane.
Classify the following molecules of as either enantiomers, chiral, achiral or
meso forms.
Locate the planes of symmetry, if any, and assign the
corresponding configurations (R) or (S).
CH3
CH 3
Cl
H
Cl
H
CH3
CH3
CH3
Cl
H
H
Cl
Cl
H
H
Cl
H
Cl
Cl
H
CH 3
5 CH3
CH3
Dr. V.O. Nyamori
(First Year Chemistry Co-ordinator) CHEM 120: ORGANIC CHEMISTRY: WORKSHEET 3
Some of the objectives

Know what homolytic and heterolytic fission is and when each would occur.

Know the significance of a full arrowhead and half an arrowhead and when
to use each.

You must know what a carbocation is.

Be able to use arrows to show bond cleavage in a molecule.

Know how radicals react to form bonds.

Know how cations and anions react to form bonds.

Know what nucleophiles and electrophiles are and be able to give examples
of each.

Be able to identify nucleophiles and electrophiles in a reaction.

You must know how the carbonyl group reacts with nucleophiles and be
able to write a mechanism for this reaction.
Problems
1. Write reactions to show bond cleavage in each case:
CH
3
OH
CH3 F
HO
OH
Cl
Cl
H
2. How many electrons are around carbon in each of the following species:
CH3
CH3
CH3
6 CH4
Dr. V.O. Nyamori
(First Year Chemistry Co-ordinator) 3. Identify the electrophile and nucleophile in the following reaction:
BCl3 + NH3 → Cl3BNH2
4. Identify each of the following species as an electrophile or a nucleophile:
I-, H+, BF3, OH-, CH3+, CH3-, H2O
5. Write down the mechanism for the following reaction and identify the product
that forms:
O
1. CN-
C
H3C
CH3
2. H+
7 Dr. V.O. Nyamori
(First Year Chemistry Co-ordinator) CHEM 120: ORGANIC CHEMISTRY: WORKSHEET 4
Some of the objectives 
Be able to write a mechanism for the halogenation of alkanes.

Be able to explain this free radical mechanism and be able to identify the
initiation, propagation and termination steps.

Be able to explain why a radical is a highly reactive species.

Be able to explain the order of stability for 1°, 2° and 3° radicals.

Be able to explain how different groups stabilise or destabilise the radical.

Be able to write a mechanism for the hydrohalogenation of an alkene.

Be able to predict and explain why, which of two possible products will be
formed in the greatest yield.

Be able to explain why and know under what circumstances, enantiomers
will form in electrophilic addition reactions.

Know what substrates and reagents are involved in an ozonolysis reaction.

Be able to predict the products of an ozonolysis reaction.

You must know the conditions under which ozonolysis reactions occur.
Problems
1. Write down the mechanism for the formation of CH3CH2Br from the reaction of
Br2, CH3CH3 and light (hv).
Identify the initiation, propogation and
termination steps and briefly explain what occurs at each step.
2. What order of stability would you predict for a) 1°, 2° and 3° carbocations; b)
1°, 2° and 3° carbanions. Explain your answer in each case.
3. Label each of the following carbocations as 1°, 2°, 3° or methyl carbocation
and then arrange them in order of increasing stability (least stable to most
stable).
CH3+;
CH3CH2+;
(CH3)3C+;
8 (CH3)2CH+
Dr. V.O. Nyamori
(First Year Chemistry Co-ordinator) 4. Label each of the carbon radicals as 1°, 2°, 3° and then arrange them in order
of increasing stability (least stable to most stable).
(CH3)3C
CH3CH2
(CH3)2CH
5. Which of the following carbocations is the more stable, ClCH2CH2+ or CH3CH2+.
Explain your answer.
6. Write down the mechanism for the following reaction and predict which of the
two possible products will be formed in the greatest yield.
Write down the
structures of the two possible products and explain your answer.
CH3
CH CH2
+
HBr
7. For each of the following reactions listed below,
(a) write down the mechanisms,
(b) write down the major and minor products in each case, and
(c) indicate which of the products in (b) above would be enantiomers.
H3C
C C
H3C
H3C
C C
H
H3C
C C
H3CH2C
H
HBr
CH3
H
HBr
CH3
CH3
HBr
CH3
8. The following alkene is first treated with a) O3 at -78° C followed by Zn and
H2O and then with b) O3 at -78° C followed by H2O2.
H3C
H
C
C
CH2CH3
H
Write down the products that would form in each case.
9 Dr. V.O. Nyamori
(First Year Chemistry Co-ordinator) 9. Write down the reagents and reaction conditions for the following reactions:
H
H
C
C
CH3
H
CH2CH3
H
H 3C
C
H 3C
C
H
H3C
CH2CH3
H 3C
C O
H3C
+
H3CH2C
C O
HO
+
H3CH2C
C O
C O
10. Write down the structure of the missing substrate in the following reactions:
1. O3, -78oC
H3C
1. O3, -78oC
2. H2O2
C O
H
2. Zn, H2O
H3C
+
H3CH2C
H3C
HO
10 HO
C O
+
H3CH2C
C O
C O
Dr. V.O. Nyamori
(First Year Chemistry Co-ordinator) CHEM 120: ORGANIC CHEMISTRY: WORKSHEET 5
Some of the objectives

Be able to recognise when an oxidation or a reduction occurred by looking
at the substrates and the products of the reaction.

You must know the oxidising and reducing agents described in the module
and what substrates they will oxidise or reduce as well as what products
will be formed in each case.
Problems
1. For each of the following reactions, suggest suitable reagents that could be
used. Indicate whether the reaction is an oxidation or a reduction reaction.
CH3CH2CH2OH
CH3CH2C
CH3CH2CHOH
CH3CH2C
H3C
H3 C
CHCH2OH
CH3CH2C
OH
O
CH3
H3 C
O
H3 C
O
C
CH3
O
CHC
H
CH3CH2CH2OH
OH
OH
H2 C
CH3CHCH3
CHCH3
11 Dr. V.O. Nyamori
(First Year Chemistry Co-ordinator) 2. Write down the products for the following reactions.
LiAlH4
CH3CH2C
O
H
CrO3/H+
H2/Pd
H2O/H+
CH3CH CHCH3
Br2
HCl
H2/Lindlar's catalyst
H3C
C
H2/Pd
C CH3
12 Dr. V.O. Nyamori
(First Year Chemistry Co-ordinator) CHEM 120: ORGANIC CHEMISTRY: WORKSHEET 6
Some of the objectives

You must know what general elimination reactions and what SN1 and SN2
reactions stand for. How many molecules are involved in the ratedetermining step of each of these SN1 and SN2 reactions.

You must know the mechanisms for SN1 and SN2 reactions.

You must know on what substrates each of these reactions can occur and
what mechanism a strong or a weak base would favour.

Be able to explain why SN1 mechanisms cannot occur for primary alkyl
halides but can occur for secondary and tertiary alkyl halides.

Know how (a) the carbocation and (b) an electronegative atom affect the
acidity of the alpha hydrogen and what the consequences of this are.

Be able to identify the nucleophile, the electrophilic centre and the leaving
group in a substitution reaction.

Be able to determine which of two groups is the better base and be able to
predict whether a substitution reaction will occur or not. If a reaction can
occur, you must be able to predict the product.

For nucleophilic substitution reactions, you must be able to predict when
inversion of configuration takes place and when retention of configuration
takes place.
Problems
1. Write down the following elimination reactions and predict the product in each
case.
CH3CH2CH2Br
NaOCH2CH3
H 2O
CH3CHCH3
Br
13 Dr. V.O. Nyamori
(First Year Chemistry Co-ordinator) NaOCH2CH3
CH3CH2CHCH2CH3
Br
Br
H2O
CH3CH2C(CH3)2
H2O
CH3CH2CH2Br
2. Write down SN2 mechanisms for the following reactions:
CH3Cl
NaOH
+
CH3CH2Cl
+
NaNH2
3. Draw the transition state for the reactions in 2 above.
4. How
many
reactants
are
involved
in
the
formation
of
the
reaction
intermediate in (a) an SN1 type reaction; (b) an SN2 type reaction?
5. Which of the following reactants will be able to undergo SN1 type reactions?
Give reasons for your answer.
(a) CH3CH2Cl
(b) CH3CH(CH3)Cl
(c) CH3C(CH3)2Cl
(d) (CH3)3CCH2Cl
6. Write down the products of the following substitution reactions.
14 Dr. V.O. Nyamori
(First Year Chemistry Co-ordinator) NaBr
NaOCH3
CH3OH
+
CH 3CH2Br
+
CH3CH2NH2
+
CH3CHCl
CH3
7. Indicate which of the products in 6 above would occur with retention of
configuration. Explain why.
15 Dr. V.O. Nyamori
(First Year Chemistry Co-ordinator) CHEM 120: ORGANIC CHEMISTRY: WORKSHEET 7
Some of the objectives

You must know why carboxylic acids, alcohols and terminal alkynes are
weak acids and the consequences this has in organic reactions.

Be able to predict when a strong base is required to remove the hydrogen
of a weak acid.

Be able to explain why alcohols and amines are bases in organic chemistry
and what consequences this has for organic reactions.

You must know why protonating the oxygen in alcohols leads to
substitution reactions whereas protonating the nitrogen in amines does
not.
Problems
1. In which of the two molecules below would a strong base be needed to
remove the proton. Explain your answer.
OH
(CH3)3C OH
pKa = 18
pKa = 10
2. Add reagents to carry out the following reaction:
CH3CH2Br
CH3C CCH2CH3
3. How could the following molecule be synthesised from the given substrate?
Write down reactions to show your answer.
HC
H3C
CH
CHC CCH2CH3
H3C
16 Dr. V.O. Nyamori
(First Year Chemistry Co-ordinator) 4. Verify that trifluoracetic acid (pKa 0.2) is a stronger acid than HF (pKa 3.2).
O
F3CC OH
trifluoracetic acid
5. Which of the following molecules would be a better nucleophile, CH3NH2 (pKa
of CH3NH3+ is 10.7) or CH3OH (pKa of CH3OH2+ is -2.5)?
6. Would ethanol react with sodium ethoxide under neutral conditions? If not,
explain why, and suggest what can be done to make the reaction work.
17 Dr. V.O. Nyamori
(First Year Chemistry Co-ordinator)