Unit 7 Covent bonding & organic chemistry
1. What are Covalent compounds
a. Covalent compounds have covalent not ionic bonds
b. Covalent Bonds- a bond formed when atoms share one or more pairs of
electrons
i. Covalent bonds are usually formed between two nonmetals with a low
electronegativity difference.
ii. The atoms involved in covalent bonds share electrons to obtain their
octet/noble gas configuration
iii. Molecules- a group of atoms held together by covalent bonds
Methane (CH4) is a covalently bound molecule:
Carbon needs 4 electrons to obtain stability
C
Hydrogen needs 1 electron to obtain stability
H
If 4 hydrogen atoms share their electrons with 1 carbon atom, then carbon will have 8 electrons
and it will be stable, and each hydrogen will have 2 electrons and it will be stable
H
H
C
H
H
Electrons are shared not donated as in ionic compounds because the electronegativity
difference between the two elements isn’t great enough for one element to steal electrons
away from the other
2. What are the different types of covalent bonds?
a. Single Bonds – Share 1 pair (2e-) of electrons.
i. When two atoms share a single pair of electrons it is represented as a
single dash in the Lewis dot structure
b. Double Bonds – Share 2 pairs (4e-) of electrons.
i. When two atoms share two pairs of electrons it is represented as two
dashes in the Lewis dot structure
c. Triple Bonds – Share 3 pairs (6e-) of electrons.
i. When two atoms share a three pairs of electrons it is represented as three
dashes in the Lewis dot structure
3. What are the properties of covalent bonds?
a. Molecular substances that consist of covalently bound atoms have a low melting
point, they are usually brittle, and they have a strong odor,
b. Because there are charged ions molecular substances are poor conductors of
electricity.
c. because atoms in carbons family can bond so many times, covalent compounds
can form isomers
d. Isomers- Molecules that are made out of the same atoms but are different 3
dimensional shapes
i. Even through the formulas of isomer molecules are exactly the same, the
unique three dimensional shape of an isomer gives it unique sets of
chemical and physical properties like boiling point
Isomer (C8H18)
CH3-CH2-CH2-CH2-CH2-CH2-CH2-CH3
Number of branches
0
Boiling point
125oC
1
117oC
3
99oC
a. As you can see, even though all the isomers have the same formula, the more
branches they have the lower the boiling point of that isomer
2. How covalent compounds are represented
a. There are three ways to represent organic molecules:
i. Molecular/chemical formula – describe the number and type of atoms in
the molecule
1. In a molecular formula the atoms are listed in C, H, O, N order
C2H6O
CH4ON2
CHN
ii. Structural formula – describes the way the atoms In the molecule are
linked together
1. Every covalent bond in a structural formula is indicated with a
dash
2. in compounds that have a lot of carbon, sometimes a skeletal
formula is used in p[lace of a structural formula
3. skeletal formulas don’t draw hydrogen and replace carbons with
kinks
iii. Valance dot diagram – shows the atoms in the molecule share electrons.
4. How do you go from a formula to a name with a covalent compound?
a. First check to see if it is a covalent compound be seeing if it is a metal bound to a
nonmetal or two non metals bound together
i. If it is two non metals then it is probably covalent
ii. If it is metal bound to a non metal than it is ionic
iii. If there is a polyatomic anion involved then it is ionic
b. Covalent compounds are all named with prefixes that tell how many of each
type of atom are present in the molecule:
Mono- = 1 atom
Hexa- = 6 atoms
Di- = 2 atoms
Hepta- = 7 atoms
Tri- = 3 atoms
Octa- = 8 atoms
Tetra- = 4 atoms
Nona- =9 atoms
Penta- = 5 atoms
Deka- = 10 atoms
c. The only time you don’t use a prefix is if there is 1 of the first atom:
Photsphorous triodide = PI3
VS.
Diphosphorous trioxide = P2O3
Write the formula of the following covalent compounds
carbon monoxide
phosphorus tribromide
carbon tetrachloride
diphosphorus trioxide
nitrogen trichloride
5. How do you go from a name to a formula with a covalent compound?
a. First determine if it an ionic or covalent compound:
i. If it’s a metal bound to a non metal its ionic
ii. If its two non-metals bound together its covalent
b. Simply write the symbol for each element in the order it appears with a subscript after that
corresponds to the prefix
i. Remember the only time you don’t use a prefix is if there is one of the first element
Name the following covalent compounds:
SiO2
SO3
SiF4
N2O
PCl3
1. Organic Chemistry
a. Organic Chemistry- “carbon” chemistry, the study of those substances made up of carbon.
i. Since most of the molecules organisms use to live are made out of carbon, the study of
molecules containing carbon is in a way studying the chemistry of life
ii. Hydrocarbons- molecules made out of carbon and hydrogen
1. All hydrocarbon molecules have a carbon chain as their backbone
a. Carbon Chain- in hydrocarbon molecules carbon atoms may link-up to
form large molecules with this as their “backbone.”
2. How to name organic compounds
a. To name organic compounds you first have to count and number the carbons in the backbone
b. Then use a prefix to indicate the number of carbons in the backbone
i. Meth = 1 carbon
ii. Eth = 2 carbon
iii.
iv.
v.
vi.
Prop= 3 carbon
But- = 4 carbon
Pent- =5 carbon
Hex- = 6 carbon
vii.
viii.
ix.
x.
Hept- = 7 carbon
Oct- = 8 carbon
Non- = 9 carbon
Dec- = 10 carbon
c. Use a suffix to indicate if the hydrocarbon is situated or had double or triple bonds
i. –ane = all carbons are single bond to each other
ii. –ene = one or more carbons are double bound to each other
iii. –yne = one or more carbons are triple bound to each other
d. Last right the number of the carbon that the double or triple bond takes place, and or the
functional group
Ethyne
Ethane
Butane
Ethene
1-butene
2-butene
2. What are alkanes?
a. Alkanes – a hydrocarbon molecule that consists of only single bonded carbon atoms.
iv. Each carbon is covalently bonded to 4 other atoms in an alkane.
v. Alkanes are considered to be a saturated hydrocarbon as each carbon atom is bonded to
a maximum number of other atoms (4).
1. The simplest alkane is methane CH4, however you can begin to get a longer and
longer carbon chain and surround it by carbon atoms
2. To determine the chemical formula of any Alkane Series Pattern obeys the
equation: CnH2n+2
Ex) C2H6 C3H8
C35H
3. What are Alkenes
a. In some hydrocarbon molecules, carbon atoms bond to 3 other atoms, not four.
i. Alkenes – a hydrocarbon molecule that consists of a single or multiple carbon with double
bonds
1. The general formula for Alkenes is Cn H2n
a. Ex) C3H6
C18H36
C50H100
Alkane
Vs
Alkene
Vs.
2. With alkenes there are even more opportunities to have isomers
4. What are Alkynes
a. In some hydrocarbon molecules, carbon atoms are bond to 2 other atoms, not four.
i. Alkynes – a hydrocarbon molecule that consists of a single or multiple carbon with a triple
bond
1. In a triple covalent bond there are 6 electrons shared between the two bonding
atoms.
a. General formula for Alkynes is CnH2n-2
b.
Ex) C3H4
C18H34
C50H98
5. What happens when carbon forms a ring?
a. Organic molecules don’t only have to be chains they can also be rings
i. Cycloalkanes- are single-bonded hydrocarbons in rings
Vs.
b. When rings are unsaturated (have a double bond) they are called aromatic compounds
i. Aromatic compounds – unsaturated carbon rings
6. Functional groups
a. Organic molecules are recognized by their functional group,
i. Functional group - which is an atom or group of atoms that imparts characteristic
properties to the organic molecules.
1. There are 4 different functional groups that involve an oxygen atom
a. Alcohols
b. Ethers
c. Esters
d. Carboxylic acids
7. Alcohols
a. Alcohol - functional group, that consists of oxygen bound to hydrogen on one side.
H2
i. Alcohols are represented as -OH.
C
H3C
OH
Methanol
H3C CH2 OH
Ethanol (ethyl alcohol)
CH3CH2CH2OH
1-propanol
H2C
CH2
H2C
CH
CH2
OH
cyclohexanol
ii. Chemical and physical properties of alcohols:
1. Alcohols have an odor that is often described as “biting” and as “hanging” in the
nasal passages.
2. Alcohols are also polar
8. Ethers
a. Ether- functional group that consists of a oxygen bound to a carbon on both sides
i. Ethers are represented by –O- .
ii. Chemical and physical properties of ethers
iii. Chemical and physical properties of ethers
1. Ethers tend to be non-polar
2. Ethers has have a low melting point
9. Carboxylic Acid
a. Carboxylic Acid- a functional group, that consists of a carbon atom that has a double covalent bond
to one oxygen atom and a single covalent bond to an alcohol
i. Carboxylic acids are represented by -COOH
ii. Carboxylic acids chemical and physical properties
1. Carboxylic acids are polar
2. High boiling point
3. Weak acids
4. Strong and volatile Oder
10. Ester
a. Ester- a functional group, that consists of a carbon atom that has a double covalent bond to one
oxygen atom as well as an ether
i. Esters are represented by -COO- group attached.