Intro to Org Chem Flashcards
How to assign O.N. to struc of the compound
what’s the ave O.N. of C in CH3(CH2)2OH
Bonding e- are assigned to the more electro-ve atom (gains 1 e-, ON decreases by 1)
If a bond is formed b/w 2 atoms of the same element, both atoms have the same electro-vity, no gain/lose of e-
Ans: 1/3 (-3-2-1) = -2
3 types of hydrocarbons
Aliphatic hydrocarbons - open chains of C atoms
- str. chain hydrocarbons (saturated C-C, unsaturated C = / 三 C)
Alicyclic hydrocarbons - closed ring of C atoms (cyclo…)
Aromatic hydrocarbons - contains benzene ring
Characteristics of homologues (5)
- can be represented by a general formula
- differs from the successive member by a CH2 grp
- shows a grad change in phy properties such as bp
- similar chem properties
- can be prepared by similar methods
Classes of compounds | homologous series | struc of func grp | general formula | eg
Hydrocarbons | alkane | - | Cn H2n+2
Hydrocarbons | alkene | C=C | Cn H2n
Hydrocarbons | alkyne | C 三 C | Cn H2n-2
Halogen derivatives | halogenoalkane | -X (X = Cl, Br, I) | RX | chloroethane
Halogen derivatives | halogenoarene | benzene ring - X | - | chlorobenzene
Hydroxy compounds | alcohol | -OH | R-OH | ethanol
Hydroxy compounds | phenol | benzene ring -OH | - | phenol
O
|| Carbonyl compounds | aldehyde | - C - H | with a R | ethanal
O
|| Carbonyl compounds | ketone | - C - | with 2 R | propanone
O
|| Carboxylic acid & derivatives | Carboxylic acid | - C - O - H | with R | ethanoic acid
O
|| Carboxylic acid & derivatives | Ester | - C - O - | with 2 R | methyl ethanoate
O
|| Carboxylic acid & derivatives | Acyl/acid halide | - C - X | with R | propanoyl chloride
H
|| Nitrogen compounds | Amine | - N - H (pri amine) | with a R | ethylamine
O H
|| || Nitrogen compounds | Amide | - C - N - H (pri amide) | with a R | propanomide
H H O
| | || Nitrogen compounds | Amino acid | H - N - C - C - O (pri amine) | same | alanine | |
R H Nitrile | - C 三 N | R - C 三 N | propanenitrile
Defn of a functional grp
Is made up of an atom or a grp of atoms within the org compound that is responsible for its characteristic chemical properties
Defn of a homologous series
Family of compounds having the same functional grp
Types of formula (3 -> 4)
Empirical - simplest ratio of the diff types of atoms
Molecular - shows actual no.
Structural
~ Displaced/full structural - show every atom, but C & H atoms in rings are not shown
~ Condensed - show how grps of atoms are Sequentially arranged, bond lines are omitted except for rings, ( ) around similar grps bonded to the same atom
~ skeletal - shows carbon skeleton with any func. grps, H atoms attached to C are not shown (those attached to O are tho)
~ Stereochemical - show spatial 3D struc
‘—-‘ same plane
‘ ||||| ‘ into paper
‘ coloured triangle’ coming out of paper
How to draw skeletal formula
Straight chain are in /\/\/\/\ format
when drawing single bonds, direction is irrelevant (turning thingy)
how to draw double n triple bonds
when heteroatoms (atoms other than C & H) are bonded to a carbond skeleton, it must be joined directly to the carbon EXCEPT for alkyl grps ( H on the right of C)
How to name compounds (5 steps)
Prefix(es) Root Suffix
Step 1: suffix n root
Suffix = principal func grp (IF there’s >1 func grp, the one with higher priority is listed as the suffix - others as prefix)
Root = select longest continuous C chain, containing the prin. func. grp & C-C multiple bond (if any)
Meth | eth | prop | but | pent | hex | hept | oct | non | dec
(Maggie escaped prison by plane…)
Add cyclo in front for an alicyclic system
- ethane = ethene 三 ethyne
Step 2: Identify prefixes Step 3: Positional no. (1) lowest-principal func grp (2) lowest - C-C multiple bond (3) lowest - position of substituent (if there's a few, the sum should be lowest)
Step 4: string prefixes together
If same sub. appears, add di-, tri-, tetra-
add appropriate positional no.
list prefixes in alphabetical order
commas separate no., - separate no. & words
Step 5: everything together
3 - animo - 2 - chloro - 4,4,5 - trimethylheptanoic acid
Defn of isomerism
refers to the existence of 2 or more compounds with the same molecular formula but diff arrangements of the atoms in their molecules. These compounds are known as isomers.
Types of isomerism (2->3,2)
Constitutional isomerism: Chain isomerism. positional isomerism, functional grp isomerism
Stereoisomerism: Cis-trans isomerism, enantiomerism
Defn of stereoisomerism
Existence of 2 or more compounds with the same molecular formula and structural formula but diff spatial arrangement of atoms
2 conditions for cis-trans isomerism + general formula for no. of cis-trans isomers in a compound + how abt C=C in ring struc?
- Restricted rotation abt a bond either by the presence of a double bond OR ring struc
- For an alkene, each C in the C=C bond must have 2 diff grps attached to it. For a cyclic compound, 2 or more C atoms in the ring must each have 2 diff grps attached to them
[no cis-trans for double bond in ring, only OUTSIDE the ring]
If the no. of C=C bonds is n, the max no. of cis-trans isomers for the compound is 2^n
Cis-trans also possible for N=N, C=N
Cis VS. Trans for bp & mp
Cis-but-2-ene (*C shape):
Higher bp - slightly higher polarity (net dipole moment),
Lower mp - fits into crystalline lattice more poorly
Cis & Trans have similar chem properties (just react at diff rates), but diff physical properties
2 Conditions for enantiomerism
Forms a non-superimposable mirror image / no plane of symmetry
has chiral carbon (chiral compounds) - sp3 hybridised with 4 diff grps attached to it
