Virtual Vista science 20 Unit A chapter 3 conclusion

carbon-based compound

a compound primarily made up of carbon atoms

organic chemistry

the study of compounds composed of carbon

hydrocarbon

an organic molecule containing only carbon & hydrogen atoms

Alkane

a fully saturated hydrocarbon consisting of only single carbon-carbon bonds, equation: C_nH_2n+2 where the +2 is the end hydrogens, and the x2 because each carbon usually holds 2 hydrogen in a chain.

Alkene

A hydrocarbon with at least one carbon double bond

equation: C_nH_2n where the lack of +2 is due to the fact two carbons share 2 electrons thus two hydrogen are remove from the equation, balancing -2 and +2 hydrogen. An electron bond takes up one spot in both valence shells, and does the work of two hydrogen.

Alkyne

A hydrocarbon with at least one carbon triple bond

equation: C_nH_2n-2 where -2 is used to denote how carbons now share a total of 3 electrons, leaving room only for one more bond for each electron. The one electron each the two hydrogens provided to the double bond are now no longer needed, as the carbons get it from each other.

continuous-chain alkane

an alkane consisting of one simple chain of carbon atoms

complete structural

diagram that uses a line to convey bonds derived from electron sharing

..h. h. h h
…|. |. |. |

h-c-c-c-c-h or c=c etc
…|. |. |. |
…h h h h

condensed structural

diagram that uses a line for carbon-carbon bonds and includes the chemical formula for carbon hydrogen bonds.

CH₃ -CH₂ etc

line structural

diagram that uses only lines for carbon-carbon bonds, where you assume the hydrogen is attached to the carbon

prefix

first syllable, in hydrocarbons it indicates # of carbons.

suffix

second syllable, indicates family (alkane has the suffix ‘-ane’)

branched alkane

Alkanes that have branches which extend from them.

alkyl group

An alkane branch of a larger molecule with one hydrogen removed. I.e the branch

What is the maximum amount of bonds a carbon atom can have?

With 4 empty spots in the valence shell, carbon can share up to 4 electrons with other atom(s). Carbon has a wide range of possible combinations with this configuration.

What is the significance of hydrogen and by association hydrocarbons?

Hydrogen only needs 1 extra electron to fill its valence shell, therefore it can easily chain with carbon.

What suffix do alkyl groups (branches) use?

The suffix: ‘-yl’. The prefix are the same as continuous chain prefixes, but with the ‘-yl’ suffix. (meth-yl, eth-yl instead of methane, ethane)

What are the steps for naming hydrocarbons?

1. find the longest chain (may not be in a straight line)

2. find all the branches & name

3. number the parent chain starting from the end nearest to a branch

4. organize branch numbers, if there are 2 methyl branches, the carbon is ‘dimethyl’

5. alphabetize, ignore prefixes (di, tri, tetra, etc). E is before M so ‘ethyl’ goes first.

A hydrocarbon with the longest chain having 7 carbon atoms (hept)

2 branches consisting of 1 carbon (di-meth)

1 branch consisting of 2 carbons (eth)

Counted from the end closet to a branch, the methyl are attached to carbon 2 and 3, and the ethyl to carbon 4 of the longest branch. Therefore:

4-ethyl-2, 3-dimethylheptane

saturated hydrocarbon

a hydrocarbon only containing single covalent bonds between carbons (another name for Alkane)

unsaturated hydrocarbon

a hydrocarbon with double/triple covalent bonds between carbons.

Fatty acid

organic molecule; chain of carbons with one COOH group at the end and a methyl group at the other. Builds up molecules of fat.

.h

• methyl : h-c-

  .h

monounsaturated fat

a fat molecule that includes fatty acids which only have one double bond.

polyunsaturated fat

a fat molecular compound that includes fatty acids which have more than one double bond

essential fatty acid

a fatty acid the body cannot make itself and must get from outside sources.

hydrogenation

process that inserts hydrogen, turning unsaturated double & triple bonds into saturated single bonds

industrially produced trans fatty acid

synthetic molecule that has hydrogen atoms on opposite sides of the bonded carbon, resulting in a straighter chain

industrially produced trans fat

a fat molecule with at least one trans fatty acid chain. Usually made with partial hydrogenation

dietary cholesterol

substance found in animals as food

How does margarine, derived from a molecule with weaker attraction, maintain a solid state at room temp?

Normally, oleic acid, because of the bend placing the molecules farther away (not able to pack as closely together), have weaker attraction therefore less energy is needed to separate them.

However, through partial hydrogenation, hydrogen is placed on either end, balancing the molecule and making it straighter, therefore the atoms pack together closer, contributing to a stronger attracting force. More energy is required to separate the bonds raising the melting and boiling point.

• trans means “on opposite sides” in latin, which is why these types of molecules are called trans fatty acids.

• cis means “on the same side” in latin
  

boiling

Transition from solid to gas

melting

Transition from solid to liquid

Why is this molecule called ‘omega-9’?

take note of the end with a methyl hydrogen group, and the end with a COOH group. Counting from the omega group— methyl— the bend (double bond) comes after the 9th carbon, hence it is an ‘omega-9’ fatty acid.

Alkene and Alkyne suffix’s?

Note: the longest chain must be made to include the bond

Alkene: ‘-ene’

Alkyne: ‘-yne’

Steps to naming bonded carbons?

1. parent chains must include bonded carbons

2. count starts from the bonded carbon, the bond must happen after the lowest carbon

why do boiling and melting points increase with amount of atoms?

Larger molecules often have greater mass and more surface area, leading to stronger and more numerous intermolecular forces. As a result, more energy is required to break apart a molecular compound.

What is the difference in volatility between saturated and unsaturated hydrocarbons?

unsaturated hydrocarbons (more than one bond between atoms) are more volatile (reactive) than saturated hydrocarbons (single bonds.

Process of hydrogenation

first, the unsaturated bonds are broken, then hydrogen is inputted into the molecule. This leads to a saturated single bond hydrocarbon.

petroleum

liquid mixture of hydrocarbons formed over millions of years from the remains of ancient microscopic marine organisms.

Petroleum fractions

Petroleum consists of groups of different length hydrocarbons, and can be separated into these group lengths, which are fractions of the total mixture.

refining

an industrial process that separates, purifies, and alters raw materials.

Fractional distillation

The petroleum “soup” is first vaporized, separating the different fractions based on their boiling points. Inside a column heated from the bottom, the vaporized fractions rise. As they move up the column, the temperature gradually decreases. When a fraction cools to a temperature slightly below its boiling point, it condenses and turns back into a liquid, allowing it to be collected. This happens because the temperature is no longer high enough to maintain the vapor state, and its too cool for the fraction to become a gas, ergo it collects as a liquid.

The lighter fractions may have a boiling point at say, room temperature, so they maintain a gas state as they rise and are collected as gasses.

Naptha

A long mixture of hydrocarbons between 5 and 10 carbon atoms, which is dense enough to collect at the bottom of column as liquid.

Cracking

breaking down leftover longer chains into short molecules. There isn’t a set way these are broken down, and can be broken down into alkene and alkyne molecules.

C₁₂H_26^dodaecane —> C₈H_18^octane + C₄H_8^butene

• If n = 4, and H=8, it must be an alkene as its formula is C_nH_2n. Also, n=4 means four carbons, so ‘but-’ prefix.

other examples:

C₁₂H_26^dodaecane —> C₁₀H_22^decane + C₂H_4^ethene

C₁₂H_26^dodaecane —> C₄H_8^butene + C₅H_12^pentane + C₃H_6^propene

The two types of cracking?

Thermal cracking: high temp and pressure. 750^o c heat, 70 atm

Catalytic cracking: low temp and pressure. Passed through a zeolite catalyst which tends to break the bonds, 500^o c

Petrochemical

a chemical made from petroleum

Combustion

a rapid reaction with oxygen that produces energy and oxides

polymerization

a reaction where short hydrocarbons join together to form longer hydrocarbon chains

polymer

the result of polymerization; a larger hydrocarbon molecule

What is the use of hydrocarbons after refining?

combusted/burned for energy

raw material for making products

Why are hydrocarbons excellent fuels?

• relatively stable & easily transported

• have bonds that store a lot of energy

• readily available

combustion

non-spontaneous reaction, requiring external energy to break bonds. The atoms recombine in different configurations afterwards. INCLUDE PIC

also: a rapid reaction with oxygen that produces energy and oxides