Intro to Organic Chemistry

Question 1

What is empirical formula?

Answer 1

• simplest formula showing the ratio of all the different atoms in a molecule

Question 2

What is molecular formula?

Answer 2

• the actual number of atoms of each element in a molecule

Question 3

What is displayed/full structural formula?

Answer 3

• drawing of all the bonds present in the molecule (including O-H bonds)
• except for ring structures like cyclohexane or benzene (leave in skeletal formula)

Question 4

What is condensed formula?

Answer 4

• atoms shown in unambiguous manner according to the bonds present in the molecule
• e.g. CH3CO2H instead of C2H4O2

Question 5

What is skeletal formula?

Answer 5

• simplified representation of a structure, often used for larger and more complicated molecules
• each C-C bond represented by 1 line
• impt. C-H bonds are omitted

Question 6

What is stereochemical formula?

Answer 6

• shows the 3D structure around a key part of a molecule
• solid wedges indicate bonds pointing out of the plane (of the paper)
• dashed wedges indicate bonds pointing into the plane
• normal lines indicate bonds that lie on the plane

more under enantiomerism

Question 7

classification of organic compunds

What are the 3 main types of organic compounds?

& their subsets if any

Answer 7

aliphatic hydrocarbons
- straight-chain vs branched

alicyclic hydrocarbons
- closed ring of carbon atoms

aromatic hydrocarbons
- compounds containing a benzene ring

Question 8

Functional groups of hydrocarbons

& their respective general formulae

Answer 8

alkane - CnH2n+2
alkene - CnH2n

Question 9

Functional groups of halogen derivatives

Answer 9

halogenoalkane - R-X

halogenoarene - benzene ring-X

X=Cl, Br. I

Question 10

Functional groups of hydroxy compounds

Answer 10

alcohol - R-OH

phenol- benzene ring- OH

Question 11

Funtional groups of carbonyl compounds

Answer 11

aldehyde - RC=OH

ketone - RC=OR’

each atom bonded to C, no O-H or O-R bonds

Question 12

Functional groups of carboxylic acids and derivatives

Answer 12

carboxylic acid - RC=OOH

ester - RC=OOR’

acyl halide - RC=OX

O in O-H and O-R’ bonds attached to C X is attached to C (X=Cl, Br)

Question 13

Functional groups of nitrogen compounds

Answer 13

amine - R-NH2

amide - RC=ONR’2

nitrile - R-CN

amino acid -HNH-HCH-COOH

N in NR’2 attached to C

Question 14

What is a homologous series?

Answer 14

a family of compounds containing the same functional group where each successive member increases by one -CH2 unit
- same general formula
- gradual change in physical properties as molar mass increases
- similar chemical properties

Question 15

Explain IUPAC

Answer 15

prefix - parent - suffix
1. Identify the longest continuous no. of C atoms (parent chain) - meth-, eth- prop-, but-, pent-, hex-. hep-, oct-, non-, dec-
2. Identify the major functional group (suffix) - -ane, -ene, -ol, -amine, -nitrile, -al, -one, -iodic acid, -oate, -oyl chloride
3. Number the C atoms (starting from the one closets to the FG, for alkanes, begin at end nearer to first branch)
4. Identify substituents on parent chain and its position (number)

list of prefixes:
minor FG
chloro-, bromo-, iodo-, (alcohol) hydroxy-, (amine) amino-, (ether) alkoxy-, (aldehyde) formyl-, (ketone) oxo-, (alkane) alkyl-, (alkene) alkeny-, nitro-, (nitrile) cyano-

list of multipliers:
presence of two or more same subs
di-, tri-, tetra-, penta-, hexa-, hepta-, octa-, nona-, deca-

Question 16

alkenes, aromatics, esters

Special cases of IUPAC

Answer 16

alkenes - position of double bond must be indicated

commonly substituted benzenes
- benzene, chlorobenzene, bromobenzene, (NO2-) nitrobenzene, (CH3-) methylbenzene, (OH-) phenol, (NH2-) phenylamine, (CN-) cyanobenzene
-* (CHO) benzaldehyde, (CO2H) benzoic acid*

esters - first part is alcohol group, second is carboxylic acid group (-oate)
RC=O R’

Question 17

Types of Organic Species

Answer 17

electrophile
- electron-deficient
- can accept a pair of electrons
- have positive charge, partial positive charge or neutral
- Br+, H+, AlCl3 (Al has vacant orbital, 6 valance electrons, to accept a lone pair of electrons)

nucleophile
- electron-rich
- can donate a pair of electrons
- have negative charge or neutral with at least one lone pair of electrons)
-NH3, H2O, OH-, CN-
- C=C double bonds and benzene rings are electron-rich FGs, can be used to attack electrophiles

radicals
- has an unpaired electron
- will accept a lone electron
-Cl-, CH3, NO2, NO
- to determine a radical, count the total no. of valance electrons, odd no. - radical

Question 18

Types of Organic Reactions

Answer 18

ADDITION
(unsaturated FG) molecule + molecule = 1 single pdt
&
ELIMINATION
large molecule = small molecule (H2O) + (unsaturated FG) molecule

CONDENSATION
molecule + molecule
= larger molecule + small molecule (HCl, H2O by-pdt)
&
HYDROLYSIS (catalysed by dilute A/B)
molecule + H2O =
molecule + molecule

OXIDATION
gain of O / loss of H
oxidation no. of C increases
&
REDUCTION
loss of O / gain of H
oxidation number of C decreases

SUBSTITUTION
replacing an atom / group withh another
R-Cl + OH- = R-OH +Cl-
CH4 + Cl2 = CH3Cl + HCl

unsaturated FGs - C=C, C=O

Question 19

Electron movement

Answer 19

Homolytic fission
- breaking of a single covalent bond, resulting in equal sharing of electrons between the 2 atoms, forming radicals
- half-headed arrow

Heterolytic fission
- breaking of a single covalent bond, resulting in unequal sharing of electrons between the atoms, forming ions
- full-headed arrow

Homolytic/Heterolytic fusion
- bond formation

electrons must always flow from electron-rich to electron-poor regions