Chem. 1B – 12/8 Lecture

Announcements I• Lab Final

– On Wed./Thurs. this week– Will be 25 questions, multiple choice– Bring green type Scantron 882E– Questions will be similar to quiz questions, pre-

lab questions, and post-lab questions• Make Up Quiz –

– Today – A and B versions– (periodic table on back – in case you can’t see it)– following announcements

Announcements II• Mastering Chemistry

– Chapter 20 questions – due 12/15– Introduction (“due” 12/16) WORTH 0 Points

• Thursday– Last Day of Class– Finish Organic Chemistry (Functional Groups)– Teaching Evaluations– Review of Material Since Exam 3

• Final Exam– Thursday, Dec. 17, 12:45-2:45 (sect. 2 to 6 here)

Announcements III• Final Exam – cont.

– Help Session (Tues. 12/15, available before 12 or after 3:30)

– Format (52 multiple choice questions – including two bonus questions – Bring Scantron SC982-E)

– All material covered is possible for questions– Less emphasis on calculations– Some questions combining sections (example

combustion of hydrocarbons combining thermodynamics and organic chemistry)

– Some questions will come from: exams, quizzes, in-class questions, or homework questions

Announcements IV• Final Exam – cont.

– I will post some example organic chemistry questions and solutions to make up quiz

• Today’s Lecture – Organic Chemistry– Alkynes– Reactions– Aromatic Compounds

Announcements V• Taking Other Chemistry Classes at

CSUS?– If your program requires you to take Chem

20, 24 or Chem 31, I recommend taking them sooner (rather than later when you have forgotten concepts learned here)

– Getting into labs (Chem 31 and Chem 25/20L) can be hard due to impaction, but can “crash” labs (a few seats are reserved for adding at beginning of semester)

Chapter 20 Organic Chemistry• Alkynes– Contain at least 1 carbon-carbon triple bond– Naming (replace –ane ending with –yne with

number referring to end of triple bond closest to the #1 carbon)

– Triple bond uses sp hybridization and leads to a linear structure

– Example:• CH3CH=CHCH3 is 2-butyne (linear)• Carbon skeleton structure

Chapter 20 Organic Chemistry• Alkynes – cont.– Alkynes are considerably more energetic

than alkenes– Used less by organic chemists (harder to

synthesize, fewer uses)– Used by Dr. Spence in ene-diyne

compounds (generates cyclic radical)

Chapter 20 Organic Chemistry• Some Basic Hydrocarbon Reactions– Combustion (all types, but alkynes generate

more energy than alkenes and alkanes generate the least energy)HxCy + O2(g) → CO2(g) + H2O(g) (unbalanced, but be able to balance)

– Halogenation of Alkanes• Example CH3CH3(g) + Cl2(g) → CH3CH2Cl(g) +

HCl(g)• Products are typically more stable than reactants

(C-X bonds are pretty stable)

Chapter 20 Organic Chemistry• Some Basic Hydrocarbon Reactions– Halogenation of Alkanes – cont.

• Occurs by “free radical” mechanism:Cl2(g) + heat or light → 2Cl•(g) (where “•” shows free

radical)Cl•(g) + CH3CH3(g) → HCl(g) + CH3CH2•(g)CH3CH2•(g) + Cl2(g) → CH3CH2Cl(g) + Cl•(g) • Free radical reactions are hard to control, so will

also produce related compounds (e.g. CH2ClCH2Cl(g))

• Syngas reactions also are free radical reactions

Chapter 20 Organic Chemistry• Some Basic Hydrocarbon Reactions– Alkene Reactions (addition to double bond)

• Hydrogenation (also works with alkynes)– Example: CH2=CH2(g) + H2(g) → CH3CH3(g)– Requires H2 at high pressure and catalyst

• Halogenation– Example: CH3CH=CH2(g) + Cl2(g) → CH3CHClCH2Cl(g)– Can also use HX (hydrohalide gas) as reactant– In this case both H and X are added to alkene carbons– CH3CH=CH2(g) + HCl(g) → CH3CHClCH3(g)

+ CH3CH2CH2Cl (g)both products possible, but only one observed

Chapter 20 Organic Chemistry• Some Basic Hydrocarbon Reactions– Alkene Reactions – Halogenation – cont.

• Why is only CH3CHClCH3(g) observed?• Markovnikov’s Rule (H added to side with

most Hs)• What is expected product of HCl(g) +

?

Chapter 20 Organic Chemistry• Questions1. Give the name for the following compounds:a) CH3CH=C(CH3)2

b) CH2=CH(CH3)CH=CH2

c) (CH3)2CHC=CH2. Predict the product of HBr(g) +

3. What type of product is produced by hydrogenation of alkenes?

a) alkanes b) alkynes c) dienes d) halocarbons

Chapter 20 Organic Chemistry• Aromatic compounds– Benzene, the simplest aromatic compound– Formula = C6H6

– Structure (see below)

=

• However, all C – C bonds are the same length (due to all sp2 hybridization which perfectly matches 120° bond angle for hexagon)

H

H

H H

H

H

Chapter 20 Organic Chemistry• Aromatic compounds – cont.– While adding double bonds makes

compounds less thermodynamically stable, benzene and other aromatic compounds (compounds containing benzene ring) are relatively stable both thermodynamically and kinetically

– Some due to “resonance stabilization”– Due to stability, reactions are different than

alkene reactions

Chapter 20 Organic Chemistry• Aromatic compounds – cont.– Substituted aromatics (benzene ring plus

substituent)– Examples of monosubstituted aromatics

methylbenzene = toluene

chlorobenzene

ClOH

hydroxybenzene = phenol

isobutylbenzene or 2-phenylbutane

Chapter 20 Organic Chemistry• Aromatic compounds – cont.– Disubstituted aromatics– Number around ring starting with earlier

(alphabetical) constituent

hydroxy before methyl so right C = #1

OH1

23

4

5 6

name = 1-hydroxy-2-methylbenzene

1, 2 disubstitution is also known as “ortho”

Cl

name = ?

1,3-disubstitution = “meta” and 1-4-disubstitution = “para”

Chapter 20 Organic Chemistry• Aromatic compounds – cont.– Substituent Naming (other than alkyl)

Substituent Name-Br Bromo--Cl Chloro--OH Hydroxy--NH2 Amino-

Chapter 20 Organic Chemistry• Aromatic compounds – cont.– Reactions: substitution reactions– Examples:

+ Cl2FeCl3

(catalyst)

Cl

+ HCl

Cl replaces H

+ CH3ClAlCl3

(catalyst)+ HCl

CH3 replaces H

Chapter 20 Organic Chemistry• More Questions1. Predict the product of the following

reactions:a) (CH3)CH=CH2 + Br2 →b) trans (CH3)CH=CH(CH3) + H2(g) →c) (CH3)2C=CH(CH3) + HBr →2. Give the names of the following compounds:

NH2

Br