Chem. 1B – 12/8 Lecture. Announcements I Lab Final –On Wed./Thurs. this week –Will be 25...
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Transcript of Chem. 1B – 12/8 Lecture. Announcements I Lab Final –On Wed./Thurs. this week –Will be 25...
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