Chapter 8 Alkenes and alkynes I.Properties and synthesis8.1 IntroductionAlkenes are hydrocarbons whose molecules contain the carbon-carbon double bond.

Hydrocarbons whose molecules contain the carbon-carbon triple bond are called alkynes.

8.2 Nomenclature of alkenes and cycloalkenes

The IUPAC rules for naming alkenes are similar in many respects to those for naming alkanesSelecting the longest chain that contains the double bondNumber the chain

3. Indicate the locations of the substituent groups

4. Number substituted cycloalkenes in the way that gives the carbon atoms of the double bond the 1- and 2- positions and that also gives the substituent groups the lower numbers at the first point of difference

5. Two frequently encountered alkenyl groups are the vinyl group and the allyl group.

6. Designate the geometry of a double bond of a disubstituted alkene with the prefixes cis- and trans-

8.2A The ( E )-( Z ) System for designation alkene diastereomers

8.3 Nomenclature of alkynes8.3A IUPAC Nomenclature

Unbranched alkynes, for example, are named by replacing the ane of the name of the corresponding alkane with the ending yne. The chain is numbered in order to give the carbon atoms of the triple bond the lower possible numbers.

8.4 Physical properties of alkenes and alkynes8.5 Hydrogenation of alkenes

8.6 Hydrogenation: The function of the catalyst

Catalytic hydrogen and Syn--addition

8.6A Syn and anti additions

8.7A Syn addition of hydrogen: Synthesis of cis-alkenes

8.7B Anti addition of hydrogen: Synthesis of trans-alkenes

8.9 Relative stabilities of alkenes8.9A Heats of hydrogenation

The order of stabilities;

8.9B Relative stabilities from heats of combustion

8.9C Overall relative stabilities of alkenes

8.10 CycloalkenesThe rings of cycloalkenes containing five carbon atoms or fewer exist only in the cis form. Therefore, fewer exist in the trans form because of the ring strain.

Cis- and trans-Cycloalkenes

8.11 Synthesis of alkenes via elimination reactions

8.12 Dehydrohalogenation of alkyl halides

8.12A E2 reactions: The orientation of the double bond in the product. Zaltsevs Rule(----

8.12C The stereochemistry of E2 reactions:

8.13 Dehydration of alcoholsThe experimental conditions----temperature and acid concentration

Ease of Dehydration

8.13A Mechanism of alcohol dehydration: An E1 reaction

Ease of dehydration for E1 reaction

8.15 Carbocation stability and the occurrence of molecular rearrangements (

The type of rearrengement

Rearrengement mechanism (E1 reaction)

8.16 Alkenes by debromination of vicinal dibromides

8.17 Summary of methods for the preparation of alkenes

2. Dehydration of alcohols

3. Dehalogenation of vic-dibromides

4. Hydrogenlation of alkynes

8.18 Synthesis of alkynes by elimination reaction

8.19 The Acidity of terminal alkynesThe hydrogen atoms of ethyne are considerably more acidic than those of ethene or ethane

Relative acidity;

Relative AcidityConjugate acid)(Conjugate base)

8.20 Replacement of the acetylenic hydrogen atom of terminal alkynesSodium ethynide and other sodium alkynides can be prepared by treating terminal alkynes with sodium amide (NaNH2) in liquid ammonia

It applied synthesis (SN2)

8.21 Other metal acetylidesEthyne and terminal alkynes also form metal derivatives with silver and copper (I) ions

As a method for separating terminal alkynes from alkynes that have an internal triple bond

Homework; 8.22, 8.24, 8.25, 8.29, 8.30Happy New Year!

Good luck for you final organic chemistry test!