Functional Groups June 6,2011

Functional groups:
-Groups are organic compounds can cantain elements other than C& H
-Most reactive oart of the molecule
-maybe a single atom(such as F, Cl, B or I) or groups of atoms

Ex. Alcohols, Halides(Halogen) or Nitro, aldehydes, ketones, Carboxylic Acids, Ethers, Amines, Amides, Esters

Halides and Nitro compounds
Halogen(Halides) and Nitro cmpounds are named similar to that of simple hydrocarbon and can be attached to alkanes, alkenes and alkynes.

The main-chain name will receive one of the following prefiexs if the appropriate group is attaced.
*Use di- tri- tetra- in front for multiple groups
Halogen                 Nitro
F=floro                  NO2=Nitro
Cl=Chloro
Br=Bromo
I=Iodo

properties of Halogenated compounds.
-compounds contain Halogen(F, Cl, Br & I are generally insoluble in water)
-fluorinated hydrocarbon are inert(unreactive)
-compounds contain Cl or Br are more reactive, but only under drastic dconditions
-compounds contain I are very reactive. I atom can easily be replaced by other functional compounds.
Ex.

 

2-chloro-1,1,2-Trifloroethane

 

Properties of Nitro Compounds(No2)

1. Normally insoluble in water.

2.Unreactive to chemical attack except under drastic conditions.

3.Tend to be explosive.

4.Pleasant odour.

 

Ex. TNT (Tri Nitro Toluene)

 

 

 

Alcohols

-An Alcohol is an organic compound that contains OH(hydroxyl) in functional group.

-Alcohols are named by

·using the longest chain contianing OH

·“E” ending changes to "Ol"

Ex. Methol   

 

 

*Count in the way that give "OH" a smaller number

 

Properties of Alcohol

-The hydroxyl group(OH) in an alcohol tends to make the type of compounds soluble in water.

The hydrocabrn chain tends to be insoluble in water.

 

All alcohol are poisonous to some degree, including C2H5, the form of alcohol present in alcoholic beverages.

 

Ex.

 

propanol

 

Multiple-OH

-if a compound has more than one -OH group number. Add -diol  -triol

 

1,2---ethandiol

 

Aldehydes & Ketones

-both are organic compounds that contain a carbonyl functional group(double boned oxygen)

 

Aldehydes:

-a compound that has doulbe bonded oxygen at the end of a chain

-change the parent ending "e" to "al"

Ex. methanal(simplest)

 

 

  butanal

 

 

Ketones:

-compound has doubled bonds oxygen that are not on either end.

Ex.

propaone.

 

 

Alkenes and Alkynes

=Double & Triple bonds of Carbon

When multiple bonds form, fewer H are attracted to C atom

The position of double/triple bond always have the lowest # put in front of the parent chain

Alkenes:

Definition: simple hydrocarbon with one or more double bonds

CH2=CH2 Ethene

CH2=CH-CH3 Propene

Geometric isomers:

Trans: opposite corner

Cis: both top or bottom

  

CH3CH2┐ ┌CH3

   C=C

CH3CH2CH2┘ └CH2CH3

Alkynes:

- Triple bonds

- naming: end with -yne

CH≡CH   Ethyne

CH≡C-CH3   Propyne

CH3-CH2-CH-C≡C-CH3

        └CH3                 4-methyl-2-haxyne

Alkene:

Alkyne



Chemical Bonding!

Chemical bonding only involves the valence e-

Formed when e- attracted by nucleus of another

Electrostatic force- opposite charge attract; like charge repel

- greater distance, smaller attraction

- greater charge, greater force.

- the force operates equally in all directions


Intermolecular force=force between molecules

Intramolecular force=force within a molecule

Only weak bonds break in melting process



Chemical bonds exhibit various degrees of sharing, depending on the amount of attraction.



Polarity=molecule's electrical balance, but imbalance with electrical charge of elements



Ionic=electrons are transferred

Non polar covalent=shared equally

- Electronegativity difference <0.5

- Attain full electron shells

- Simultaneously attracted

- high melting points(except CH4, O2, F2)

Polar covalent= shared unequally

- higher energy=partial negative charge=δ-

- lower energy=partial positive charge=δ+

- arrow indicates the migration of electrons

Example

Organic Chemistry May 26, 2011

The chemistry of carbon compounds
.

Importance
-organic compounds are seen anywhere in our life.
-Examples of organic compounds: sugar, chair.......

Properties of organic compounds.
-low melting point
-weak or non-electrolytes
-can forms chains of carbon atoms that are linked in a
①straight-line

 

②circular pattern

③branched pattern

    -can link with other atoms in:

    single bonds

  double bonds

  triple bonds

*Versatility organic compounds makes it such an important branch of chemistry.

Alkanes (unbranched/straight chain)

-A hydrogen : only contains O,H

There are different types of hydrogen

                             ways to present them

-no-polar molecules → immiscible with water

-geometry: tetrahedron

-alkanes are saturated alkanes( all C atoms are bonded by single bonds)

*Saturated: not possible for another atom to bond to the structure.

-Naming of alkanes: the names of all hydrocarbons end in "-ane"

Ex. The structure of C2H6?

①          

     full structure                     

②CH3CH2CH3  

Condensed structure

③C3H8

molecular formula

④

 

Ball-and-Stick model

Names of Alkanes.

methane   CH4

ethane      C2H6

propane   C3H8

butane      C4H10

pentane    C5H12

hexane     C6H14

heptane    C7H16

octane      C8H18

nonane     C9H20

decane     C10H22

They are homologous series: a series of organic compounds with similar general formula, possess similar properties.

CnH(2n+2) -----only for alkanes.

Branched hydrocarbons

hydrocarbons have "side branches" which are also hydrocarbon chains.

(substituted carbon/ branched carbon)

Ex

* Alkyl group: an alkane which has lost one hydrogen atom.

The bottom part are alkyl group(CH3)

 

The name of this branced hydrocarbon is 2-methylpropane

*"-pronpane" is the parent hydrocarbon(longest chain)

Carbon has 4 bonds.

  10 hydrogens

Naming: the names of all alkyl groups end in "-yl", because they are alkyl.

Ex. C2H6      ethyl  C2H5

      C3H8      propyl C3H7

Electron Dot & Lewis Diagrams

- nucleus is represented by the atomic symbol

- for individual elements, # of valence electrons

- electrons are represented by dots around the symbol

- a orbit hold a max of 2 electrons

- each orbital gains 1 electron before pair up

Each bond represents 2 electrons

All valence electron must be used

Each element must have a full valence orbital except H

Ex. CH4

Period Table Trend

Metallic Properties:
- the change from metallic to non-metallic going from left to right across the table
- elements become more metallic going down a family

Atomic Radius:
- Decreases across a row from left to right, increase down a group

Reactivity:
- metal&non-metal show different trend
- most metal: Francium
- most non-metal: Fluorine


Ion charge:
- elements ion charges depend on their group


Melting&Boiling point:
- centre of the table-->highest melting/boiling point
- noble gases have lowest melting point

Ionization Energy
- increases up and right
- hellium highest
- Francium lowest

Electronegativity:
- fluorine has highest electronegativity

- Francium has lowest electronegativity

Predicting the # of valence electron

Valence  electron:  electron which can take part chemical reactions also called the " reactable electron" in the outermost(energy level) open electron shell of atom.
-open shell: shell contains less than max. # of electron
-closed shell: contains exactly max. # of electron

valence electron: not in the core, not it d- & f- subshells

ex.
Al=[Ne]3s2 3p1  has 3 valence electron
Pb=[Xe]6s2  4f14  5d10  6p2  has 4 valence electron
Xe=[kr]5s2  4d10  5p6  or[Xe] has 0 valence electron (noble gases)

The periodic law summmarizes the period table
-The periodic law: properties of the chemical elements recur periodically when the elements are arranged from lowest to highest number.
            

ELECTRON CONFIGURATION!!

-the elctronic configuration of an atom is notation that describes the orbitals in which the electrons occupy and the total number of electrons in eaqch orbital.

-when an electron absorbs or emits a specific amount of energy it instantaneously moves from one orbital to another.

-an energy level is the amount of energy, which an electron in an atom can possess.

-energy difference between two energy level is quantom of energy.

Ground State: when all the electrons of an atom are in their lowest possible energy level.

Excited State: when one or more of an atom's electrons are in higher energy level than the lowest electron.

Orbital: an orbital is the actual region of space occupied by an electron in a particular energy level.

Shell: a shell is the set of all orbitals having the same n-value.

Subshell: a subshell is the set of orbitals of the same type.

The letters s, p, d, f refer to the four different types of orbitals, each circle represents an orbital.

For a given value of "n", different types of orbitals are possible for:
n=1 only the s- type
n=2 s- and p- types
n=3 s- , p- and d- types
n=4 s- , p- , d- and f- types.

A maximum of 2 electrons can be placed in each orbit. (Pauli Exclusion Principle)

Writing Electronic Configuration for Neutral Atoms
-always start with the lowest energy level.
-figure out how many electrons you have, then start at the lowest (1s) and keeping adding.
-each electron has an opposite spin designated by upward and downward arrows.

ex. C has 6 electrons, 2 in the 1s, 2 in the 2s and 2 in the 2p.
notice the 2 electrons in the 2p pccupy separate suborbitals and are not paired up.
the electron configuration is 1s2 2s2 2p2.

Writing Electronic Configuration for Ions
for negative ion:
-add electron to the unfilled subshell, starting where the neutral atom left off.

for positive ion:
-start with neutral atom, remove electron from the outermost shell first.
-in both s- and p- , remove from p-, first.

Core Notation
the set of electrons for an atom can be divided into two subsets: the core electrons and the outer electron.
-the core of an atom is the set of electron with the configuration of the nearest noble gas that comes before it.
-the outer electron consist of all electron outside the core electron normally take part in chemcal reactions.

locate the atom and note the noble gas at the end of the row ABOVE the element.

ex. S: 1s2 2s2 2p6 3s2 3p4
          [NE] 3s2 3p4

 

Atomic Structure~

proton: has a relative mass of 1 and electric charge of +1; located in the nucleus.
neutron: has a relative mass of 1 and no electric charge; located in the nucleus.
electron: has a relative mass of almost 0, has a electric charge of -1; located in the cloud surrounding the nucleus.


Atomic number=the proton number


Atoms have no overall electric charge. Therefore, # of p+ = # of e-
anion: when e- is added to an atom
cation: when e- is removed from a atom.


Mass number= # of proton + # of neutron. (therefore, # of neutron = mass # - # of proton)
Atomic mass= the average mass of a element's isotopes


Isotope: have same atomic number but different atomic mass (in another word, different # of neutron)

Atomic Theory

Atomos: Smallest pieces
-matter was made of four different combinations: Earth, Air, Fire, Water
-turn common metal into gold
-marked the beginning of the understanding of matter

Four elements theory lasted for about 200 years
not a scientific theory because it could not be tested against observations

Democritus

-300bc, atoms are invisible particles

-first mention of atoms

-not a textual theory, but conceptional

-no mention of atomic nucleus, or constituents

-not used to explain chemical reaction

Lavoisier

-first version of the law of conservation of mass and law of definite proportions.

-recognized and named Oxygen gas(1778) and Hydrogen gas(1783)

Proust

-if a compound is broken down into its constituents, the products exist in the same ratio as in the compound.

-proved Lavoisier Laws

Dalton

-Atoms are solid, in destructive spheres

-provides for different elements

-based of law of conservation of mass

5 main points

--Elements are made of atoms

all atoms of a given elements are identical

different from other elements; distinguished by relative weights.
atoms can be combined with others of different elements to form chemical compound
given compound has same relative numbers of types of atoms.
atom: indestructive. chemical reaction only changes the way atoms are grounded together.

J.J.Thomson
-raisin bun model
-solid,positive spheres with negative particles embedded them
-first atomic theory to have +(P+) and -(e-) charges
-demonstrated the existence of e-
-Crookes's tubes and other equipments, J.J.Thomson discovered e- and measured the ratio.

Ruther ford
-atoms have a positive dense censer with e- outside
-planetary model
-explain why e- spin around nucleus
-atoms are mootly empty space

Neils Bohr
-studied gaseous samples of atoms, glow by possing an electric current through.
-e-surrounded the nucleus in specific "energy levels" or "shells"

The Modern Art
-atom is the smallest particle
-made up 3 kinds of particles called subatomic particles
Proton(p+)
neutron(n0)
electron(e-)

PERCENT PURITY!!

Sometimes, the reactant(s) we use is/are not pure.  So, before we can calculate much product will form, we need to use PERCENT PURITY to calculate how much reactant that actually is available to react.

% PURITY=Mass of Pure Substance/Mass of Impure Sample×100%

Below is a link of a video that demonstrates one example of the percent purity.
http://www.youtube.com/watch?v=15FOjmIUEy4&playnext=1&list=PL45C0C062682A839A

 

PERCENT YIELD!!

Sometimes, it is not possible to recover all the product, or not all the reactions are used up, and therefore, we need to calculate PERCENT YIELD.

PERCENT YIELD=the ratio of amount of product obtained to amount of product expected by claculated, expressed as a %.

% YIELD=grams of actual product recovered/grams of product expected from stoich×100%

ex. HBrO3+5HBr→3H2O+3Br
if 10.0g of HBrO3 is reacted with excess HBr and 26.3g of Br2 was prodeced, what is the percent yield?
10×(1mole/128.9g)×(3mole/1mole)×(159.8g/1mole)=37.191g Br2

%YIELD=26.3g/37.191g×100%=70.7% yield

ex. C3H6Cl2+2KSCN→C3H6(SCN)2+2KCl
the % yield is 80%.  how many grams of C3H6(SCN)2 will be produced if 3.00 grams of C3H6Cl2 is reacted with excess KSCN?
3g×(1mole/113g)×(1mole/1mole)×(158g/1mole)=4.20g C3H6(SCN)2

% YIELD=C3H6(SCN)2 obtained/420g expected×100%=80.0% yield
C3H6(SCN)2=3.36g

          

Excess & Limiting Reactants persent yield

A.Excess Quantity
A balanced equation describes what should happen in a chemical reaction.

However, the conditions necessary for the reaction to take place may not be present. (ie. pressure, temperature, concentration etc.)

Sometimes it is necessary to add more of one reactant than the equation predicts because it is not possible for every atom/molecule of the reactants to come together.
Ex. One reactant is the Excess Quantity and some of it will be left over, the second reactant is used up completely, and is the limiting reactant.

B.Excess quantities in chemical reactions.
Ex1. How many grams of OCl2 will be formed when 44.0 g of O2 reactant with 97.0g of Cl2

(*General Process: Convert both reactants to the desired product & the smaller amount of product will actually be produced.)

Step1: Balanced equation.
O2(g) +2 Cl2(g) → 2OCl2(g) 

Step2: Convert Cl2 to OCl2
97.0 g ×1mol Cl2/71g × 2mol OCl2/2mol Cl2 × 87.0g/1mol OCl = 118.86 g OCl2

Step3: Convert O2 to OCl2
44.0g × 1molO2/32g ×2mol OCl2/1mol O2 × 87.0g/1mol OCl = 239.25g OCl2
Because 97.0g of Cl2 reacts to produce the smaller amount of product. Cl2 is limiting quantity and O2 is excess quantity. 119g is the mass of product.

Ex2. 
41g O2 reacts of 164g of Cl2, Which is EXCESS quantity? Which is Limiting quantity? How many grams of the excess quantity will be used?
Step1:
O2(g) +2 Cl2(g) → 2OCl2(g) 
41.0g       164g
(*General process: Convert ONE of products to the other reactant to see which excess and which is limiting. Determine which is left over and by how much. It may involve another conversation)
Step2:
To find which reatant is in excess calculate how many grams of Cl2 gas would be required to react with 41.0g of O2.
41g O2 × 1mol O2/32.0gO2 × 2mol Cl2/1mol H2 × 71.0g Cl2/1mol Cl2= 181.93g=182g Cl2

Since there are only 164g of Cl2 gas, not all O2 can react. Thus Cl2 is limiting quantity and O2 is excess quatity.

Step3: Convert Cl2 to O2 to see how much O2 would be needed to react with 164g of Cl2.
164g Cl2 × 1mol Cl2/71.0g Cl2 × 1mol O2/2mol Cl2 × 32.0g/1mol O2 = 36.958=37.0 g O2

37.0g of O2 would react with 164g of Cl2.

STOICHIOMETRY (2) !!

Example 1 :
a) How many grams of Fe(Ⅱ) will be needed to react with 3.20 mol of HCl?

Step1: Balance the equation.
1Fe + 2HCl → 1FeCl2 + 1H2

Step2: Make a "ROAD MAP"

Step 3: Do calculation

3.2 mol HCl × 1mol Fe/ 2mol HCl × 56g Fe/ 1mol Fe = 90g Fe

b) How many grams of Fe will be needed to produce 10.0 g H2

10.0 g × 1mol/2.0 g H2 × 1mol Fe/ 1mol H2 × 56 g Fe/1 mol Fe =280 g Fe

Note: grams (X) ↔ mol(x) ↔ mol(y) ↔ grams(y)

Example 2 :

a) Using the following equation : 2 NaOH + 1H2SO4 → 2H2O + 1Na2SO4

How many grams of sodium sulphate will be formed if you start with 200 grams of sodium hydroxide?

200 g NaOH × 1mol NaOH/ 40 g × 1mol Na2SO4/2 mol NaOH × 355.3g Na2SO4/ 1mol = 888.25 g

                                                                                                                                            = 900 g