Download Chapter 4: Carbon

Chapter 4: Carbon
Fall 2012
Carbon
•
•
•
•
Although cells are 70-95% water, the rest consists mostly of carbon-based compounds.
Carbon forms the backbone of proteins, fats, carbohydrates, and nucleic acids
We all eat at the SPONCH CaFé (but not in that order…HOCNCaPSFe is just too hard to pronounce!!)
Percentages don’t vary much from one organism to another.
However, because of carbon’s versatility, these few elements can be combined to build an inexhaustible variety of organic
molecules.
Organic Chemistry
•
•
Organic chemistry is the study of carbon containing molecules
This includes carbon-containing molecules that are derived from nonliving sources.
– Organic compounds can range from simple molecules, such as CO2 or CH4, to complex molecules, like proteins.
A carbon atom
•
•
•
Carbon’s atomic number is 6. This means it has 4 valance electrons.
It has little tendency to form ionic bonds by loosing or gaining 4 electrons.
Instead, it usually completes its valence shell by sharing electrons with other atoms in four covalent bonds.
• This tetravalence by carbon makes large, complex molecules possible.
Organic molecule: Building Code
•
•
•
•
•
Commit to memory the valances for the 4 major organic elements:
Carbon = 4, Nitrogen = 3; Oxygen = 2, Hydrogen = 1;
Also remember that carbon can bond to itself and can form double bonds to nitrogen, oxygen and carbon atoms
These give you the basic rules for how organic bonds are made.
Examples
Carbon Dioxide – CO2
• Urea – CO(NH2)2
•
Hydrocarbons
– Chains of various length (Ethane vs. Propane)
– Location of Double Bonds (1-Butene vs. 2-Butene)
– Branching (Butane vs. 2-methylpropane)
– Rings (cyclohexane vs. benzene)
Significance of Hydrocarbons
•
•
•
•
•
•
Hydrocarbons are the major component of petroleum
Regions of molecules in our cells consist of hydrocarbons
Hydrocarbons are nonpolar and therefore, hydrophobic
The bonds in a hydrocarbon store lots of energy that is released upon burning.
Isomers
An isomer is a compound that has the same numbers of atoms of the same elements but a different structure and different
properties
3 kinds of isomers:
– Structural
– Geometric
– Enantimers
Structural Isomers
•
•
Differ in the covalent arrangement.
Number of isomers increases as you increase the size of the carbon skeletons
•
3 isomers of C5H12
•
18 isomers of C8H18
•
366,319 isomers of C20H42
Geometric Isomers
•
•
•
•
•
Isomers that have the same sequence of atoms but differ in the spatial arrangement of atoms due to the presence of a
double bond.
Enantiomers
Molecules that are a mirror image of each other.
Middle carbon is asymmetrical (attached to 4 different atoms or groups of atoms)
Designated L and D for left (levo) and right (dextro)
They can’t be superimposed on each other
Functional Groups
•
•
•
•
Functional groups are organic molecules that attach to hydrocarbons and are commonly involved in chemical reactions.
Think of it as a generic “person” who can take on different identities with different hats.
Each functional group behaves consistently from one organic molecule to the next.
There are SIX functional groups
Hydroxyl (-OH)
•
•
Polar covalent bond between oxygen and hydrogen and between oxygen and the rest of the molecule. Makes this group
very soluble in water
Molecules with a hydroxyl group are alcohols and their names end in –OH
Carbonyl (-CO)
•
•
•
Oxygen double bonded to the carbon chain.
In the middle of the molecule it‘s called a ketone
On the end of the molecule, it’s called an aldehyde
Carboxyl (-COOH)
•
•
Oxygen is double bonded to a carbon that is also bonded to a hydroxyl group.
Acids because the H on the OH will rapidly dissociate.
Amino (NH2)
•
•
•
Nitrogen bonded to two hydrogen atoms and to the carbon skeleton
Called Amines
Amino acids have both and amino group and a carboxyl group
Sulfhydryl (-SH)
•
•
•
•
•
•
Sulfur bonded to hydrogen and also bonded to the carbon skeleton
Called Thiols
Two sulfhydryl can interact to stabilize proteins; this structure is called a disulfide bridge
Phosphate -OPO32Oxygen bonded to the carbon skeleton and phosphate.
Phosphate also bonded to 3 more oxygens
Makes whole molecule an anion because it so rapidly loses H ions leaving a negative charge behind.