naming alkynes · hint 1. naming alkynes alkynes are named similarly to alkenes in that the...

10/4/2018 Assignment 4 Task 2

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Assignment 4 Task 2Due: 11:59pm on Friday, October 5, 2018

You will receive no credit for items you complete after the assignment is due. Grading Policy

Chapter 9 Reading Quiz Question 1

Part A

What is the correct IUPAC name of the following compound?

Hint 1. Naming alkynes

Alkynes are named similarly to alkenes in that the lowest-numbered multiply bonded C atom is specified in the name. In terms of chain numbering, atriple bond is equal in priority to a double bond, of greater priority than a halogen or alkyl group, and of lower priority than a hydroxyl group. See 9-2.

ANSWER:

Correct

Naming Alkynes

Learning Goal:

To understand the conventions used in naming alkynes.

Hydrocarbons are molecules that consist entirely of carbon and hydrogen atoms and are classified by their bond structure:Hydrocarbon Bond structure

alkane carbon-carbon single bonds

alkene at least one carbon-carbon double bond

alkyne at least one carbon-carbon triple bond

Rules for naming hydrocarbons

Alkynes are named using the yne ending and with prefixes to indicate the number of carbon atoms in the longest carbon chain. The position of the triple bond isindicated with a number designating the position of the bond in the carbon chain. The numbering starts at the end of the carbon chain closest to the triple bond.For example, or is called 2-butyne.

The roots used to indicate the number of carbon atoms are given in the table below.Number of atoms 1 2 3 4 5 6 7 8 9 10

Root name meth eth prop but pent hex hept oct non dec

Part A

What is the name of the following organic compound?

Spell out the name of the compound.

Hint 1. How to approach the problem

First, determine how many carbon atoms are present in the compound and find the appropriate root. Second, determine whether any triple carbonbonds are present and find the appropriate ending. Finally, note the location of any triple bonds by placing the appropriate number in front of thecompound name.

Hint 2. Count the carbon atoms

How many carbon atoms are present in the compound?

Express your answer numerically as an integer.

7-chloro-2-methylhept-1-en-5-yne




C C≡CCH3 H3 C CCCH3 H3

C

C C CCC C CH3 H2 H2 H2 H3



ANSWER:

Hint 3. Find the appropriate root name

What is the appropriate root for the number of carbon atoms in this compound?

Spell out the root name.

ANSWER:

Hint 4. Locate any multiple bonds

What kinds of bonds are present in this molecule?

Hint 1. Finding unsaturated carbon atoms

A hydrocarbon molecule is said to be saturated when it contains only single bonds. Each carbon atom can form a total of four bonds, witheach bond formed either with another carbon atom or with a hydrogen atom. A hydrogen atom can only form a single bond with a carbonatom in a hydrocarbon molecule.

An unsaturated carbon atom forms one or more double or triple carbon-carbon bonds. A carbon atom that is involved in a double or triplebond with another carbon atom has fewer bonds to spare for binding to hydrogen atoms. Therefore, you can deduce the bond structure ofthe hydrocarbon by looking at how many hydrogen atoms are bound to each carbon atom.

ANSWER:

Hint 5. Determine the class of the hydrocarbon

Look at the bond structure. What kind of hydrocarbon is this?

ANSWER:

Hint 6. Find the location of the triple bond

What is the number of the first carbon atom in the triple bond?


ANSWER:

ANSWER:

Correct

Part B

7number of carbon atoms =

hept

This molecule contains only single bonds.

This molecule contains one double bond.

This molecule contains one triple bond.

an alkyne

an alkene

an alkane

3

3-heptyne



Draw the structure for 1,5-dichloro-3-hexyne.

Draw the molecule on the canvas by choosing buttons from the Tools (for bonds), Atoms, and Advanced Template toolbars. The single bond isactive by default.

Hint 1. Determine the number of carbon atoms in the main carbon chain

How many carbon atoms are in the main carbon chain of 1,5-dichloro-3-hexyne?


ANSWER:

Hint 2. Determine the class of the hydrocarbon

What kind of hydrocarbon is 1,5-dichloro-3-hexyne?

ANSWER:

ANSWER:

Correct

Problem 9-28 - Enhanced - with Feedback

Give IUPAC names for the following compounds.

You may want to reference (Page) Section 9.2 while completing this problem.

Part A

6number of carbon atoms =

an alkane

an alkene

an alkyne



Spell out the full name of the compound.

ANSWER:

Correct

This compound contains a triple bond and should be named as an alkyne using the -yne suffix. The parent chain contains five carbons with thetriple bond at the carbon-2 position in the chain. Assigning the phenyl substituent based on the position of the triple bond, which has priority, thename of this compound is 5-phenyl-2-pentyne or 5-phenylpent-2-yne.

Part B


ANSWER:

Correct

This compound contains both double and triple bonds, and should be named as an alkenyne. The double and triple bond should be assignedusing the smallest pair of counting numbers possible since they have equal priority, and the configuration of the unsymmetric double bond shouldbe designated using the E/Z system. The molecule also has a methyl substituent which should be specified as well. The name of this compoundis (Z)-3-methyl-2-hepten-4-yne or (Z)-3-methylhept-2-en-4-yne.

Part C


ANSWER:

Correct

This compound contains a triple bond and should be named as an alkyne using the -yne suffix. There are three methyl groups that need to bespecified, and using the smallest counting number possible to assign the triple bond, the name of this compound is 2,2,6-trimethyl-3-heptyne or2,2,6-trimethylhept-3-yne.

Part D


ANSWER:

Correct

The name of this compound is 5,5-dibromo-2-pentyne or 5,5-dibromopent-2-yne.

Part E

5-phenyl-2-pentyne

(Z)-3-methyl-2-hepten-4-yne

2,2,6-trimethylhept-3-yne

5,5-dibromopent-2-yne




ANSWER:

Correct

This compound contains both a triple bond and alcohol functional groups and should be named as an alkynol using both the -yn and -ol suffixes.Since the alcohol functionality has priority over the triple bond, the compound should be named using the smallest counting number possible toassign the alcohol and all other substituents and functionalities assigned based on that designation. The name of this compound is 3-methyl-4-hexyn-3-ol or 3-methylhex-4-yn-3-ol.

Part F


ANSWER:

Correct

This compound has a triple bond and cyclopentyl substituent, so the name of this compound is 1-cyclopentyl-2-butyne or 1-cyclopentylbut-2-yne.

Acidity: Complete the statement about the stability of the alkane, alkene, and alkyne compounds based onhybridization

Part A

Drag the appropriate labels to their respective targets. Use only pink labels for pink targets.

ANSWER:

3-methylhex-4-yn-3-ol

1-cyclopentylbut-2-yne



Correct

Ethyne contains hybridized atoms. The high s-character of an hybridized orbital makes the bonding electrons more drawn towardsthe more electronegative atoms. The electron deficient hydrogen atoms bonded to the atoms in ethyne or terminal alkynes are easilyremoved by strong bases.

Acidity: Rank neohexene, t-butylacetylene, and di-t-butylacetylene in order of acidity

Part A

Rank the following compounds from least acidic to most.

Rank from least acidic to most acidic. To rank items as equivalent, overlap them.

ANSWER:

HelpReset

sp C sp C−HC C

Reset Help

The correct ranking cannot be determined.

ethene

ethane

sp2

sp3

ethyne

sp

most acidicleast acidic



Correct

The internal alkyne has only bonds, so it is the least acidic; the alkene has a bond; and the terminal alkyne has a bond, so it is the most acidic.

Alkynes: Reaction of sodium propynide with 1-chloropentane

Part A

Draw the organic product formed when the structure shown below undergoes a reaction with CH3C≡CNa.

Interactive 3D display mode


ANSWER:

Correct

The C-Na bond dissociates to give a carbanion, which participates in an SN2 substitution on the alkyl halide to make a new C-C bond.


C(s )−Hp3 C(s )−Hp2

C(sp)−H



Part A

Which of the following alkenes would yield an alkyne upon addition of Br2, followed by reaction with more than two molar equivalents of NaNH2?

Hint 1. Synthesis of alkynes by elimination reactions

Recall that alkynes can be prepared by double E2 elimination of vicinal or geminal dihalides. See 9-8.

ANSWER:

Correct

Alkyne: Reaction of 3-heptyne with HCl

Part A

Draw the structure of the product that is formed when the compound shown below undergoes a reaction with two equivalents of HCl. There is more thanone correct answer, but draw just one product.



ANSWER:

A

B

C

D



Correct

Addition of HCl takes place according to Markovnikov's rule.

Alkynes: Choose the right reagents to synthesize hexanal from 1-hexyne

Part A

Choose the right reagent or series of reagents from the ones listed below to prepare hexanal from 1-hexyne.

ANSWER:

Correct

Water will add to the triple bond in an anti-Markovnikov fashion, and an enol will be formed. This will further tautomerize to a carbonyl compound.

Alkynes: Hydration of hex-2-yne

Part A

Hydration of alkynes (via oxymercuration) gives good yields of single compounds only with symmetrical or terminal alkynes. Draw the major organicproduct(s) formed when hex-2-yne undergoes hydration in the presence of HgSO4 and H2SO4.

disiamylborane followed by , H2 O2 HO−

(2 equiv)HCl

, Lindlar cat. followed by , H2 OH2 H+

, followed by , NaNH2 OH2 H+

, , OH2 SH2 O4 HgSO4




Draw the molecule(s) on the canvas by choosing buttons from the Tools (for bonds), Atoms, and Advanced Template toolbars. The single bondis active by default.

ANSWER:

Correct

adds across one of the bonds, and the enol tautomerizes to the ketone. There is no strong preference to add to either side of the alkyne,so two products are obtained.

Alkynes: Reaction of 2-butyne with H2, cat. Pt

Part A

Draw the major product that is formed when 2-butyne is treated with an excess of hydrogen gas and a platinum catalyst.


ANSWER:

OH2 π



Correct

The reduction of alkynes with H2 over Pt gives alkanes.

Alkynes: Reaction of 2-butyne with H2, Lindlar catalyst

Part A

Draw the major product that is formed when 2-butyne is treated with hydrogen gas and Lindlar catalyst.


ANSWER:



Correct

The hydrogenation of alkynes over Lindlar catalyst gives cis alkenes.

Alkynes: Reaction of 2-butyne with Na and liquid NH3

Part A

Draw the major product formed when 2-butyne undergoes a reaction with Na in liquid NH3.


ANSWER:



Correct

Alkynes are reduced to trans alkenes under these conditions.

Alkynes: Reaction of but-2-yne with Br2 (1 equivalent)

Part A

Draw the structure of the product that is formed when the compound shown below undergoes a reaction with one equivalent of Br2.



ANSWER:



Correct

Br2 adds across a triple bond in anti fashion.


Part A

What would be the major product of the following reaction?

Hint 1. Metal–ammonia reduction

Alkynes can be partially reduced to alkenes by treatment with an alkali metal (commonly Na or K) in liquid ammonia. The mechanism involves twosequential electron transfer–proton transfer steps.

ANSWER:



Correct


Part A

What is the major product of the following reaction?

Hint 1. Halogenation of alkynes

The addition of HBr to the pi bonds of alkynes occurs sequentially and in accordance with Markovnikov's rule. See 9-9D.

ANSWER:

Correct

Score Summary:Your score on this assignment is 99.3%.

You received 15.89 out of a possible total of 16 points.

A

B

C

D

A

B

C

D

naming alkynes · hint 1. naming alkynes alkynes are named similarly to alkenes in that the...

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