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Kimia Organik

1. Structure and Bonding review (11/11)2. Classes of Organic Compounds (11/11)3. Aliphatic Hydrocarbons (11/11)4. Aromatic Hydrocarbons (18/11)5. Chemistry of the Functional Groups (25/11-

9/12):• Alcohol & Ethers• Aldehyde & Ketones• Carboxylic Acids & derivates

6. Chemical Analysis and Instrumentation (an Introduction) (16-23/12)

IntroductionOrganic chemistry is the chemistry of the compounds of carbon.Inorganic Chemistry: the chemistry of the other ~100 elements.Carbon can form more compounds due to its ability to form not only single, double or triple C-C bonds, but also to link up with each other in chains and ring structures.Over 13 million synthetic and natural organic compounds are known – significantly greater than so known inorganic compoundsOrganic chemicals, those from living organisms (animal, vegetable) were complex and contained C, H, and often N and/or O.Inorganic chemicals (mineral) were simpler, could contain a variety of elements, but only rarely carbon, except for carbonates.covalent bonding- sharing electrons- most common bonding in organic compounds

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How to handle variety

nomenclature - clear methods for naming structures and reactions structures - organized by functional groups reactions - organized by reaction types (what happens?) reactions - organized by reaction mechanisms (how does it happen?)

Classes of organic compounds

distinguished according to functional groups they containa functional group is a group of atoms that is largely responsible for the chemical behavior of the parent moleculeall organic compounds are derived from hydrocarbons because they are made up of only H and C

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Classes of organic compounds

aliphatic hydrocarbons do not contain benzene group/ring

aromatic hydrocarbons contain one or more benzene rings

Hydrocarbons

Aliphatic Aromatic

Alkanes Cycloalkanes Alkenes Alkynes

Structure and Bonding review

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Resonance

more than one possible Lewis structure for a compound What's the best Lewis structure? follow the octet rule electronegativity determines the best place to locate chargescarbon monoxide (CO)nitromethane (CH3NO2)

Resonance structure

If one can draw more than one reasonable Lewis structure for a molecule, then that molecule is a hybrid of the structures which may be drawn. Each contributing Lewis structure is a resonance or canonical structure.

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Resonance Rules

1. All nuclei must be in the same location in every resonance structure; they cannot move.

2. Each resonance structure must have the same number of unpaired electrons (eg, 0, 1, 2, etc.).

Molecular Geometry From Lewis Structures –electron pair repulsion model

Count the number of "electron groups" around the atom. Each unshared pair counts as one group, as does each bond whether single or multiple.If there is more than one resonance structure, use the one with the greater number of bonds attached to the atom in question.

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sp3

sp2

sp

Functional Groups

characteristic arrangement of atoms that define a family of compounds R represents generic carbon group alcohols: R-O-H ethers: R-O-R carbonyl group ( C=O )

aldehydes: RCHO ketones: R2CO

carboxyl group ( COO )

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Polar Bonds to Carbon

C-C bonds are nonpolarC-H bonds are generally considered nonpolarC-X bonds are polarized with carbon d+for X = F, Cl, Br, I, O, S, N C-M bonds are polarized with carbon d-for M = metals

Writing Organic Structures

Lewis structures- all electrons shown Kekule structures- show bonds as lines- lone pairs sometimes omitted line structures- omit lone pairs- omit hydrogens on carbons- omit carbons(assumed to be at the end of every bond)

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3-Dimensional Structuresdotted-line / wedge ball-and-stick space-filling

Visualizing chemical structures

name (common or systematic) condensed formula (as usually typed out) Lewis structure (all atoms and bonds shown) line structure (omit hydrogens, assume carbons at vertices) 3-D structure (show bond orientations) ball-and-stick structure (like a molecular model you could make) space-filling model (approximates full size of electron distribution)

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Metana, CH4

Cari penggambaran struktur bensen dan penisilin

Alkanes (alkana)general formula: Cn H2n+2 , n=1,2, …..only single covalent bonds are presentalso known as saturated hydrocarbonsbecause they contain the maximum number of hydrogen atoms that can bond with the number of carbon atoms presentCarbons are sp3 hybridized.Bonds are σ-bonds. C-C bonds ~ 1.54Å; C-H bonds ~ 1.10Å. Bond angles ~ 109o.

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CH4, methane (metana)the simplest alkanenatural product of the anaerobic bacterial decomposition of vegetable matter under water --- marsh gasTermites are a natural source of methane by digestively breaking down cellulose (from wood) – estimated 170 million tons production annuallySewage treatment processes also produced methaneCommercially obtained from natural gas

Natural gas is a mixture of methane, ethane, and small amount of propaneThe structure of methane, ethane and propane are straightforward – there is only one way to join C atomsButane, C4H10 has 2 possible bonding schemes structural isomers n-butane and isobutane

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isomersStructural isomer: molecules that have the same molecular formula but different structuresin the alkane series, as the number of C atoms increases, the number of structural isomers increases rapidlybutane – 2 isomers; decane (C10H22) – 75 isomers and C30H62 has over than 4x108 isomers

Tentukan berapa isomer struktur pentana, C5H12 dan gambarstrukturnya

The first 10 Straight-Chain Alkanes

174,0-29,710CH3 – CH2 - CH3Dekana150,8-53,59CH3 – CH2 - CH3Nonana125,7-56,88CH3 – CH2 - CH3Oktana98,4-90,67CH3 – CH2 - CH3Heptana68,7-95,36CH3 – CH2 - CH3Heksana36,1-129,85CH3 – CH2 - CH3Pentana-0,5-138,34CH3 – (CH2)2 - CH3Butana

-42,1-189,73CH3 – CH2 - CH3Propana-88,6-183,32CH3 - CH3Etana

-161,6-182,51CH4Metana

BP (oC)

MP (oC)

number of C

formulaname

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Alkane nomenclaturebased on recommendation of the International Union of Pure and Applied Chemistry (IUPAC)

1. Nama utama berdasarkan rantai karbon terpanjang2. Rantai alkana kekurangan 1 atom H disebut gugus

alkil, rantai cabang disebut gugus alkil3. Jika 1 atau lebih atom H diganti gugus lain, nama

senyawa harus menunjukkan lokasi atom C tempatpenggantian tersebut

4. Pemberian nomer atom C rantai karbon terpanjangsedemikian rupa sehingga memberikan nomer lebihkecil untuk semua atom C bercabang

5. Jika ada lebih dari 1 cabang alkil yang samadigunakan awalan di-, tri-,tetra-, … mengikuti namaalkil.

6. Jika ada 2 cabang alkil berbeda, diberi nama sesuaigugus alkil diawali dengan nomer atom C posisicabang tersebut

7. Penamaan dengan cabang unsur mengikuti aturannomer 6

Common alkyl groups

t-butil

Isopropil- CH2 – CH2 - CH2 - CH3n-butil

- CH2 - CH2 - CH3n-propil

- CH2 - CH3Etil

- CH3Metil

RumusNama

CH3

- C – CH3

CH3

- C - H

CH3

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Functional groups

Vinil- CH = CH2

Nitro- NO2

Iodo-IBromo-BrKloro-ClFluoro-FAmino- NH2

NamaGugus fungsional

Beri nama senyawa berikut sesuaiIUPAC

Gambarkan struktur senyawa 2,2-dimetil-3-etilpentana

CH3

CH3 – C – CH2 – CH – CH2 – CH3

CH3

CH3

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Aliphatic hydrocarbon• alkanes• cycloalkanes• alkenes• alkynes

StrukturproyeksiNewman

proyeksiSawhorse

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Reaksi kimia alkana• Pembakaran

– sangat eksotermis

• Halogenasi alkanaalkil halida– substitusi 1 atau lebih

atom H oleh atom halogen

• campuran gas metanadan klor dipanaskan diatas 100 oC atau diiradiasicahaya dengan λ tertentu

)(2)(2)(2)(4 22 lggg OHCOOCH +→+ kJH 4,8900 −=∆

)(2)(2)(2)(62 6472 lggg OHCOOHC +→+ kJH 31190 −=∆

)()(3)(2)(4 gggg HClClCHClCH +→+metil klorida

)()(22)(2)(3 glgg HClClCHClClCH +→+Jika tersedia gas klor berlebih:

metilen klorida

)()(3)(2)(22 glgg HClClCHClClCH +→+kloroform

Apakah nama sistematik (sesuai aturan penamaan) untuk metil klorida, metilen kloridadan kloroform?

HXRXXRH panasUV +⎯⎯⎯ →⎯+ /2

Alkil halida• Kloroform

– cairan volatil untuk anastesi– toksik thd ginjal, hati dan jantung dilarang

• Karbon tetraklorida– cairan pembersih noda minyak pada kain– toksik

• Metilen klorida– solven untuk de-kafeinasi kopi dan pembersih

cat• Klorofluoro karbon

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Sikloalkana• Definisi: alkana yang rantai karbon dihubungkan

sebagai suatu cincin• Rumus umum: CnH2n, n= 3,4,…..• Yang paling sederhana adalah siklopropana• Merupakan kandungan kimia senyawa

kolesterol, testosteron, dan progesteron• Mempunyai 2 geometri berbeda

– chair– boat

chrysanthemic acidpenarik serangga

cortisone (a steroid)

strain pada sikloalkanasudut dalam poligon = 180(n-2)/n, n jumlah sisi poligon (von Baeyer)

in fact, prediksi Baeyer BENAR untuk cincin 3 dan 4 yang mempunyaienergi stabilisasi lebih tinggi daripada cincin 5 atau 6 TETAPI geometricincin >5 bukanlah PLANAR,sudut dalam C>5 mendekati sudut ideal tetrahedral, 109o C5 dan C6 banyak ditemui secara natural

C5C6 C8

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Penamaan sikloalkana

metil siklopentana 1 siklo propil butana

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Penamaan sikloalkana

1,3 dimetil sikloheksana 1,5 dimetil sikloheksana

NOT

alkena

• disebut juga olefin• mempunyai sekurang-kurangnya 1 ikatan

rangkap C=C• Rumus umum Cn H2n n=2,3,4,……• Alkena paling sederhana : C2H4 (etilen

atau etena)• Ada di alam cukup banyak

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alkena di alam• etilen gas yang berperan dalam proses

kematangan buah• α-pinena komponen utama terpentin• β-karoten pigmen oranye pemberi

warna wortel, sumber vit A dan memberiperlindungan terhadap penyakit kanker

α-pinenaβ-karoten

etilen

Tata namaalkena• nama senyawa menunjukkan posisi ikatan rangkap C=C

• nama senyawa induk/utama berakhiran dengan –ena• nama senyawa induk/utama ditentukan berdasarkan rantai C terpanjang• angka pada nama alkena menyatakan atom C bernomer paling rendah

pada rantai yang mengandung ikatan rangkap C=C• nama harus menyatakan isomer geometriknya jika ada• penamaan sikloalkena mengikuti alkena dengan penomeran atom C

sedemikian rupa sehingga ikatan rangkap terletak diantara C1 dan C2, dan gugus fungsi/substituen pertama berada pada posisi nomer C paling kecil

C=CC-CH2-CH3

CH3

H

CH3

H

C=CH

CH3

C-CH2-CH3

CH3

H

4-metil-cis-2-heksena 4-metil-trans-2-heksena 1-metil-sikloheksena

1,5-dimetil-siklopentena

1,4-sikloheksadiena

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Beberapa penamaan karena faktor sejarah, namun diterima oleh IUPAC:• etena etilen• lihat tabel

Reaksi pada alkena• Preparasi alkena Cracking

– dekomposisi termal senyawa hidrokarbon rantai panjang menjadisenyawa-senyawa yang lebih kecil (rantai pendek)

• Reaksi adisi (reaksi 2 senyawa untuk menghasilkan 1 produktunggal) – hidrogenasi– halogenasi

Preparasi alkena• via termal cracking gas alam (alkana C1-

C4) dan gasolin rantai lurus (C4-C8)

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Halogenasi dan hidrogenasi

• HALOGENASI aturan MarkovnikovC2H4 + HX CH3CH2X

C2H4 + X2 CH2X – CH2X

propilena + HBr 2-bromo propana dan atau 1-bromo propana

etilena + Br2 1,2 dibromo etana

hidrogenasi

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TINGKAT STABILITAS:tetrasubstituted > tri-substituted > di- substituted > mono-substituted

isomer geometri alkenesrotasi metil di sekitar C-C free, tidak

demikian dengan di sekitar C=C sehingga struktur yang diperoleh tidak

bersifat mudah interkonversi tanpapemutusan ikatan

kemungkinan terbentuknya isomer geometri

ikatan π putus sementara supayarotasi C-C dimungkinkan energi

barier ≥ energi ikatan π ~268 kJ/mol

NO

YES

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stabilitas isomer geometrialkena

• cis diklor etilen

• trans-diklor etilen

C=C

Cl

H

Cl

H

C=C

Cl

H

H

Cl

µ= 1,89 D

µ= 0 D

BP = 60,3 oC

BP = 47,5 oC

I. Aliphatic hydrocarbon –alkynes

II. Aromatic hydrocarbon

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Alkynes = Alkuna• Hydrocarbons that contain a C-C triple bond

• Paling sederhana, asetilen H-C≡C-H

• The triple bond consists of an sp-sp s-bond and two p-bonds.

• The remaining sp orbital on each carbon is oriented 180o

from the former sp orbital and forms a s-bond with another atom.

Bonding

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Reactions of alkynes• Reduction to an alkene

– Geometrical isomerism possible for product, except when alkyne is terminal (has triple bond at end).

Each of these reactions is stereoselective in that each yields predominantly one stereoisomer of two or more possible ones.

• Reduction to an alkane

• Addition of Halogens

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• Additions of Hydrogen Halides

Hydration of alkynes -tautomerism

• Usually the equilibrium favors the ketone (or CH3 - CHO, when the alkyne is acetylene) an acid - base equilibrium; -OH is a stronger acid than -CH3.

• Structural isomers which exist in equilibrium with each other are called tautomers.

• The particular type of tautomerism shown above is keto - enoltautomerism.

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Acidity of Alkynes – Alkynes in Synthesis —• In general, it is possible to convert a terminal

alkyne to an anion by removing the terminal hydrogen usually accomplished by using a base which is stronger than an acetylide anion:

• The acetylide anion can be used in synthesis, to make larger molecules, by reacting it with alkyl halides in a substitution reaction:

• Example problem 1 –• Synthesize 2-hexyne from starting materials

which do not contain more than 3 carbons.

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Tatanama• mengikuti aturan seperti pada alkana dan

alkena, akhiran –una• posisi ikatan rangkap tiga dinyatakan oleh atom

C pertama di dekat ikatan• penomeran atom C rantai utama sedemikian

rupa sehingga nomer C ikatan rangkap sekecilmungkin

6-metil-3-oktuna

Tatanama• Jika ada lebih dari 1 ikatan rangkap 3 diuna,

triuna, dst.• Senyawa dengan 2 macam ikatan rangkap

enuna– penomeran C dimulai dari ujung C plg dekat

sembarang ikatan rangkap; double bonds nomernya lebih rendah drpd triple bonds

1-hepten-6-una

4-metil-7-nonen-1-una

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Ring structures aromatic rings• when carbons are arranged at the corners of a

hexagon with a hydrogen bonded to each carbon and alternating double bonds between carbons

• the most basic ring structure is benzene (C6H6)• H- substituted by functional groups variety

different molecules• hydrocarbons based on the benzene ring arenes

– eg. benzene, toluene, naphtalene

• 1825, Michael Faraday isolated a new hydrocarbon from illuminating gas, which he called “bicarburet of hydrogen.”

• 1834, Eilhardt Mitscherlich of the University of Berlin prepared the same substance by heating benzoic acid with lime and found it to be a hydrocarbon having the empirical formula CnHn.

benzin

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• Many trees exude resinous materials called balsams when cuts are made in their bark some are fragrant – exotic oil

• Gum benzoin is a balsam obtained from a tree that grows in Java and Sumatra.

• “Benzoin” is a word derived from the French equivalent, benjoin, which in turn comes from the Arabic luban jawi, meaning “incense from Java.”

• Benzoic acid is itself odorless but can easily be isolated from gum benzoin.

• Compounds related to benzene were obtained from similar plant extracts.– tolu tree tolu balsam; 1840 found that distillation of tolu

balsam methyl derivative of benzene called toluene

Benzene• Benzene is very unreactive

– • It gives substitution and not addition products

– only one monobromination product of benzene was ever obtained all the hydrogen atoms of benzene are equivalent.

• Substitution of one hydrogen by bromine gives the same product as substitution of any of the other hydrogens.

– • It combines only with very reactive (usually cationic) electrophiles

WHY ????

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• 3 premises of August Kekulé (1866)1. Benzene is C6H6.2. All the hydrogens of benzene are equivalent.3. The structural theory requires that there be four bonds to each carbon.

• Kekulé advanced: Four bonds to each carbon could be accommodated by a system of alternating single & double bonds with one hydrogen on each carbon.

• low reactivity of benzene and its derivatives reflects their special stability.

• Kekulé was wrong: Benzene is not cyclohexatriene, nor is it a pair of rapidly equilibrating cyclohexatriene isomers.

• 20 centuries later new electronic theory explaining the stability of benzene’s ring

Teori Resonansi Struktur Bensena

• The two Kekulé structures for benzene have the same arrangement of atoms, but differ in the placement of electrons -- they are resonance forms, and neither one by itself correctly describes the bonding in the actual molecule.

• As a hybrid of the two Kekulé structures, benzene is often represented by a hexagon containing an inscribed circle – suggested firstly by Britain chemist: Sir Robert Robinson aromatic sextet: sextet”—the six delocalized electrons of the three double bonds.

• Robinson’s symbol is a convenient time-saving shorthand device, but Kekulé-type formulas are better for chemical reaction

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• Both Kekulé structures of benzene are of equal energy, and one of the principles of resonance theory is that stabilization is greatest when the contributing structures are of similar energy.

• Cyclic conjugation in benzene, then, leads to a greater stabilization than is observed in noncyclicconjugated trienes.

• How much greater that stabilization is can be estimated from heats of hydrogenation.

Hydrogenation of arenes in the presence of nickel requires high temperatures (100–200°C) and pressures (100 atm).

1,3 sikloheksadiena

sikloheksena

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Properties of Aromatic Compounds —• Cyclic and each atom in the ring is a π-center (uses a p atomic orbital to form π -type bonds), ie, sp2 or sp.

• Ring is flat or nearly so

• High degree of unsaturation but resistant to addition reactions –generally undergo electrophilicsubstitution (an electrophilicreagent replaces a hydrogen [usually] attached to the ring).

• Unusually stable.

• π -Electrons delocalized above and below plane of ring.

aromatic heterocycles

kina – obat malaria

sulfapiridin – antibiotikantipirin –mengurangidemam

18871938

1970s

1997

obat anti-ulcer

viagra– drug for male impotence treatment

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• p409 Carey