Practice Problems for Chapter 25: Organic Chemistry Taken from textbook Chemistry: The Central Science, 10th edition by Profs. Brown, LeMay, and Bursten

(Images may not be exactly the same as those in the textbook. Slight modifications to wording may have been made for clarification purposes.)

25.2) Which of the following molecules will most readily undergo an addition reaction?

(a) (b) (c) (d)

25.4) Which of the following compounds are capable of possessing isomerism? In each case where isomerism

is possible, identify the type or types of isomerism?

(a) (b) (c) (d)

(a) possesses isomerism; specifically this molecule has many structural isomers and also has optical

isomers due to its chiral carbon (carbon #2), which is attached to a carboxyl (COO-), a protonated amine

(-NH3+), an H, and an isopropyl group (CH(CH3)2). However, with the double bond in its current

position, this molecule would not have any geometric (cis-trans) isomers.

(b) possesses isomerism; this molecule has several structural isomers, including ortho, meta, para

isomers. However, there are no geometric isomers or optical isomers (no chiral carbons).

(c) possesses isomerism; This molecule has many structural isomers and also has geometric (cis-trans)

isomers.

(d) No isomerism

25.8) Identify the carbon atoms in the following structure shown that has (have) each of the following

hybridizations: (a) sp3, (b) sp2, (c) sp.

25.14) Give the molecular formula of a cyclic alkane, a cyclic alkene, a linear alkyne, and an aromatic

hydrocarbon that in each case contains six carbon atoms. Which are saturated and which are unsaturated

hydrocarbons?

Cyclic alkane: C6H12, saturated Cyclic alkene: C6H10, unsaturated

Linear alkyne: C6H10, unsaturated Aromatic hydrocarbon: C6H6, unsaturated

25.18) Draw as many isomers as you can for alkenes and alkynes (including cycloalkenes and dienes, as well

as any stereoisomers) with the molecular formula C6H10. (There are 56 in total. Can you get them all?)

1) 2) 3) 4) 5)

6) 7) 8) 9) 10)

11) 12) 13) 14) 15)

16) 17) 18) 19)

20) 21) 22) 23)

24) 25) 26) 27)

28) 29) 30)

31) 32) 33)

34) 35) 36)

37) 38)

39) 40) 41)

42) 43)

44) 45) 46)

47) 48) 49)

50) 51) 52)

53) 54) 55)

56)

25.22) Draw the structural formula or give the name, as appropriate, for the following:

(a) (b)

3,3,5-trimethylheptane 3,4,4-trimethylheptane

(c) 2,5-dimethylnonane

(d) 3-ethyl-4,4-dimethylheptane

(e) 1-ethyl-4-methylcyclohexane

25.24) Name the following compounds:

(a) (b) (c)

1,4-dichlorocyclohexane 3-chloro-1-propyne trans-2-hexene

(d) (e)

1-chloro-2-methyl-2-phenylbutane trans-5-chloro-1,3-pentadiene

25.32) Using condensed structural formulas, write a balanced chemical equation for each of the following

reactions:

(a) hydrogenation of cyclohexene;

+ 𝐻2 𝑁𝑖, 500℃→

(b) addition of H2O to trans-2-pentene using H2SO4 as a catalyst (two products);

+ 𝐻2𝑂 𝐻2𝑆𝑂4 → +

(c) reaction of 2-chloropropane with benzene in the presence of AlCl3

+ 𝐴𝑙𝐶𝑙3 → + HCl

25.36) The rate law for addition of Br2 to an alkene is first order in Br2 and first order in the alkene. Does this

fact prove that the mechanism of addition of Br2 to an alkene proceeds in the same manner as for

addition of HBr? Explain.

No, there can be different mechanisms that have the same rate law due to having different fast steps or

different intermediates. The rate law gives an indication of what molecules come together in the rate

determining step, however it does not take into account how those molecules come together or what

intermediates might be formed.

25.40) Identify the functional groups in each of the following compounds:

(a) (b)

(c) (d)

(e)

25.43) Give the IUPAC name of each of the following acids:

(a) (b) (c)

Formic Acid butanoic acid 3-methylpentanoic acid

Or methanoic acid

25.46) Draw the condensed structures and write the names of the esters (or amides) formed from the

combination of

(a) butanoic acid and methanol, or

Methyl butanoate

(b) benzoic acid and 2-propanol

Isopropyl benzoate

(c) propanoic acid and dimethylamine

N,N-dimethylpropanamide

25.52) Write the condensed structural formula for each of the following compounds:

(a) 3,3-dichlorobutyraldehyde,

(b) methyl phenyl ketone,

(c) para-bromobenzoic acid,

(d) methyl trans-2-butenyl ether,

(e) N,N-dimethylbenzamide,

25.54) Does 3-chloro-3-methylhexane have optical isomers? Why or why not?

Yes, the third carbon in the chain is bonded to four distinctly different groups; a methyl group, an ethyl

group, a chloro group, and a propyl group. As such, carbon #3 will be chiral and make the molecule

optically active. (See image below for labeled groups.)

25.59) (a) Draw the condensed structure of the tripeptide Ile-Ala-Cys.

(b) How many different tripeptides can be made from the amino acids serine and phenylalanine? Give

the abbreviations for each of these tripeptides, using the three-letter codes for amino acids.

8 different tripeptides can be made

Ser—Phe—Ser Phe—Ser—Ser Ser—Ser—Phe Ser—Ser—Ser

Phe—Ser—Phe Phe—Phe—Ser Ser—Phe—Phe Phe—Phe—Phe

25.64) What is the difference between α-D-glucose and β-D-glucose? Show the condensation of two

D-glucose molecules to form a disaccharide with an α linkage; with a β linkage.

An α-D-glucose has the -OH group on the anomeric carbon going in the OPPOSITE direction (up or

down) as the -CH2OH group attached to the highest number asymmetric or chiral carbon (carbon #5 on

glucose), whereas a β-D-glucose will have the -OH group on the anomeric carbon going in the SAME

direction (up or down) as the -CH2OH group attached to the highest number asymmetric (chiral) carbon.

For α-D-sugars, this generally means that the anomeric –OH group is down, and for β-D-sugars, the

anomeric –OH group is typically shown in the upward direction.

Note: The anomeric carbon is the carbon connected to 2 oxygens (in a hemiacetal group) in ring form. It

is also the carbon that contained the aldehyde in the open chain form and is the number 1 carbon.

Condensation product of two α-D-glucose molecules having an alpha linkage.

Condensation product of two β-D-glucose molecules having a beta linkage.

25.66) The structural formula for the linear form of D-mannose is as follows:

(a) How many chiral carbons are present in the molecule? 4 chiral carbons are present in the molecule.

(b) Draw the structure of the six-member-ring (pyranose) form of this sugar.

α-D-mannopyranose β-D-mannopyranose

25.70) A nucleoside consists of an organic base of the kind shown below, bound to ribose or deoxyribose.

Draw the structure for deoxyguanosine, formed from guanine and deoxyribose.

25.72) A nucleoside undergoes hydrolysis in neutral conditions to yield 1 mol H2PO4- and an organic product.

The same starting material undergoes hydrolysis under acidic conditions to yield thymine and

deoxyribose-monophosphate. Draw the structure of the unknown substance.

nucleoside starting material unknown organic product from neutral hydrolysis