Ammonia and Methylamine

Why methylamine is a stranger base than ammonia??

Answer:

The strengths of weak bases are measured on the pK_b scale. The smaller the number on this scale, the stronger the base is.

Three of the compounds we shall be looking at, together with their pK_b values are:

Remember - the smaller the number the stronger the base. Comparing the other two to ammonia, you will see that methylamine is a stronger base, whereas phenylamine is very much weaker.

Methylamine is typical of aliphatic primary amines - where the -NH₂ group is attached to a carbon chain. All aliphatic primary amines are stronger bases than ammonia.

Phenylamine is typical of aromatic primary amines - where the -NH₂ group is attached directly to a benzene ring. These are very much weaker bases than ammonia.

The only difference between this and ammonia is the presence of the CH₃ group in the methylamine. But that's important! Alkyl groups have a tendency to "push" electrons away from themselves. That means that there will be a small amount of extra negative charge built up on the nitrogen atom. That extra negativity around the nitrogen makes the lone pair even more attractive towards hydrogen ions.

Making the nitrogen more negative helps the lone pair to pick up a hydrogen ion.

Isomerism of Alkene

ISOMERS

Isomers are molecules that have the same molecular formula, but have a different arrangement of the atoms in space. That excludes any different arrangements which are simply due to the molecule rotating as a whole, or rotating about particular bonds.

Geometric (cis / trans) isomerism

These isomers occur where you have restricted rotation somewhere in a molecule. At an introductory level in organic chemistry, examples usually just involve the carbon-carbon double bond - and that's what this page will concentrate on.

Drawing structural formulae for the last pair of models gives two possible isomers.

In one, the two chlorine atoms are locked on opposite sides of the double bond. This is known as the trans isomer. (trans : from latin meaning "across" - as in transatlantic).

In the other, the two chlorine atoms are locked on the same side of the double bond. This is know as the cis isomer. (cis : from latin meaning "on this side")

How to recognise the possibility of geometric isomerism?

You obviously need to have restricted rotation somewhere in the molecule. Compounds containing a carbon-carbon double bond have this restricted rotation. (Other sorts of compounds may have restricted rotation as well, but we are concentrating on the case you are most likely to meet when you first come across geometric isomers.) If you have a carbon-carbon double bond, you need to think carefully about the possibility of geometric isomers.

What needs to be attached to the carbon-carbon double bond?

Think about this case:

Although we've swapped the right-hand groups around, these are still the same molecule. To get from one to the other, all you would have to do is to turn the whole model over.

You won't have geometric isomers if there are two groups the same on one end of the bond - in this case, the two pink groups on the left-hand end.

So . . . there must be two different groups on the left-hand carbon and two different groups on the right-hand one. The cases we've been exploring earlier are like this:

But you could make things even more different and still have geometric isomers:

Here, the blue and green groups are either on the same side of the bond or the opposite side.

Or you could go the whole hog and make everything different. You still get geometric isomers, but by now the words cis and trans are meaningless. This is where the more sophisticated E-Z notation comes in.

Conclusion

To get geometric isomers you must have:

• restricted rotation (often involving a carbon-carbon double bond for introductory purposes);
• two different groups on the left-hand end of the bond and two different groups on the right-hand end. It doesn't matter whether the left-hand groups are the same as the right-hand ones or not.

Alkane and Cycloalkane

Alkane

Hydrocarbons having no double or triple bond functional groups are classified as alkanes or cycloalkanes , depending on whether the carbon atoms of the molecule are arranged only in chains or also in rings.  Although these hydrocarbons have no functional groups, they constitute the framework on which functional groups are located in other classes of compounds, and provide an ideal starting point for studying and naming organic compounds.  The alkanes and cycloalkanes are also members of a larger class of compounds referred to as aliphatic .  Simply put, aliphatic compounds are compounds that do not incorporate any aromatic rings in their molecular structure.

The following table lists the IUPAC names assigned to simple continuous-chain alkanes from C-1 to C-10. A common "ane" suffix identifies these compounds as alkanes. Longer chain alkanes are well known, and their names may be found in many reference and text books.  The names methane through decane should be memorized, since they constitute the root of many IUPAC names. Fortunately, common numerical prefixes are used in naming chains of five or more carbon atoms.

Chemical reactivity of alkanes
Alkanes contain a strong single bond C-C and C-H bonds are also strong. C-H bond has a very low polarity so there is no molecule that carries the number of positive or negative ions to attract significant other molecules.
Therefore, alkanes have a fairly limited reaction.

Some things that can do on alkanes:
alkanes can be burned, which destroyed the entire molecule;
alkanes can be reacted with several halogen ie C-H bond break;
alkanes can be broken down, ie with a C-C bond break.

Cycloalkane

Saturated hydrocarbons occur in three forms: straight-chain forms ( alkanes ), branched chain forms ( alkanes ), and cyclic forms ( cycloalkanes ). The cycloalkanes contain only single bonds, and have the general formula C _n H _2n. Some alkanes have a continued chain ends. its called cycloalkanes, and the establishment of structures called ring. Placement of carbon in cycloalkane ring lock the carbon, so that its freedom to rotate is very limited.

Carbon bond in the smaller ring is more easily broken than in the larger ring. In the cyclopropane ring and cyclobutane, bond angle of C-C-C in a row are 60^o and 90^o. The second ring is very terikan (tense), compared with the pressure from the normal tetrahedral bond angle, namely 109^o. Consequently, the cyclopropane ring and cyclobutane very unstable compared cyclopentane or cyclohexane ring.

Chemical reaktivity of cycloalkane

Cyclialkane have very similar reactivity with alkanes, except for cycloalkane that very small - particularly cyclopropane. Cyclopropane is much more reactive. That because bond angles in the ring. Cyclopropane angle is 60°. electron pairs close together, so there repel between pairs of electrons that connects carbon atoms. This makes the bonds more easily broken.

Ethylene

Ethylene (IUPAC name: ethene) is a gaseous organic compound with the formula C₂H₄. It is the simplest alkene, Because it contains a carbon-carbon double bond, ethylene is classified as an unsaturated hydrocarbon. Ethylene is widely used in industry and is also a plant hormone.

Structure and Bonding

This hydrocarbon has four hydrogen atoms bound to a pair of carbon atoms that are connected by a double bond. All six atoms that comprise ethylene are coplanar. The H-C-H angle is 119°, close to the 120° for ideal sp² hybridized carbon. The molecule is also relatively rigid: rotation about the C-C bond is a high energy process that requires breaking the π-bond.

The π-bond in the ethylene molecule is responsible for its useful reactivity. The double bond is a region of high electron density, thus it is susceptible to attack by electrophiles. Many reactions of ethylene are catalyzed by transition metals, which bind transiently to the ethylene using both the π and π* orbitals.

Ethylene as a plant hormone

Ethylene serves as a hormone in plants. It acts at trace levels throughout the life of the plant by stimulating or regulating the ripening of fruit, the opening of flowers, and the abscission (or shedding) of leaves. Commercial ripening rooms use "catalytic generators", to make ethylene gas, from a liquid supply of ethanol. Typically, a gassing level of 500 ppm to 2,000 ppm is used, for 24 to 48 hours. Care must be taken to control carbon dioxide levels in ripening rooms when gassing, as high temperature ripening (68F) has been seen to produce CO2 levels of 10% in 24 hours.

Ethylene perception in plants

Ethylene could be perceived by a transmembrane protein dimer complex. The gene encoding an ethylene receptor has been cloned in Arabidopsis thaliana and then in tomato. Ethylene receptors are encoded by multiple genes in the Arabidopsis and tomato genomes. The gene family comprises five receptors in Arabidopsis and at least six in tomato, most of which have been shown to bind ethylene. DNA sequences for ethylene receptors have also been identified in many other plant species and an ethylene binding protein has even been identified in Cyanobacteria.

Ripe fruit will produce ethylene gas and can make a fruit not yet ripe into ripe due to it gases.

Experienced during the ripening of fruit, then the existing tissue in the fruit increased production of ethylene gases. so each fruit has a ethylene gas but the gas was increased along with the ripe fruit.

Not yet ripe fruit can be ripe because the fruit ripening ethylene gas stimulated by that diffuses into the intercellular spaces of the fruit. Gas can also diffuse through the air from one fruit to another fruit, fruit will mature more quickly if the fruit is stored in a plastic bag which resulted in accumulated ethylene gas.

Hydrocarbon

In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. The carbon to carbon can be single, double or triple. Aromatic hydrocarbons (arenes), alkanes, alkenes, cycloalkanes and alkyne-based compounds are different types of hydrocarbons. 

Types of Hydrocarbon

The classifications for hydrocarbons defined by IUPAC nomenclature of organic chemistry are as follows:

1.      Saturated hydrocarbons (alkanes) are the simplest of the hydrocarbon species and are composed entirely of single bonds and are saturated with hydrogen. The general formula for saturated hydrocarbons is CnH2n+2 (assuming non-cyclic structures). Saturated hydrocarbons are the basis of petroleum fuels and are either found as linear or branched species. Hydrocarbons with the same molecular formula but different structural formulae are called structural isomers. As given in the example of 3-methylhexane and its higher homologues, branched hydrocarbons can be chiral. Chiral saturated hydrocarbons constitute the side chains of biomolecules such as chlorophyll and tocopherol.

2.      Unsaturated hydrocarbons have one or more double or triple bonds between carbon atoms. Those with one or more double bonds are called alkenes. Those with one double bond have the formula CnH2n (assuming non-cyclic structures). Those containing triple bonds are called alkynes, with general formula CnH2n-2.

3.      Cycloalkanes are hydrocarbons containing one or more carbon rings to which hydrogen atoms are attached. The general formula for a saturated hydrocarbon containing one ring is CnH2n.

4.      Aromatic hydrocarbons, also known as arenes, are hydrocarbons that have at least one aromatic ring.

Hydrocarbons can be gases (e.g. methane and propane), liquids (e.g. hexane and benzene), waxes or low melting solids (e.g. paraffin wax and naphthalene) or polymers (e.g. polyethylene, polypropylene and polystyrene).

General properties

Because of differences in molecular structure, the empirical formula remains different between hydrocarbons; in linear, or "straight-run" alkanes, alkenes and alkynes, the amount of bonded hydrogen lessens in alkenes and alkynes due to the "self-bonding" or catenation of carbon preventing entire saturation of the hydrocarbon by the formation of double or triple bonds.

This inherent ability of hydrocarbons to bond to themselves is referred to as catenation, and allows hydrocarbon to form more complex molecules, such as cyclohexane,and in rarer cases, arenes such as benzene. This ability comes from the fact that bond character between carbon atoms is entirely non-polar, in that the distribution of electrons between the two elements is somewhat even due to the same electronegativity values of the elements (~0.30), and does not result in the formation of an electrophile.

Generally, with catenation comes the loss of the total amount of bonded hydrocarbons and an increase in the amount of energy required for bond cleavage due to strain exerted upon the molecule; in molecules such as cyclohexane, this is referred to as ring strain, and occurs due to the "destabilized" spatial electron configuration of the atom.

In simple chemistry, as per valence bond theory, the carbon atom must follow the "4-hydrogen rule",which states that the maximum number of atoms available to bond with carbon is equal to the number of electrons that are attracted into the outer shell of carbon.In terms of shells, carbon consists of an incomplete outer shell, which comprises 4 electrons,and thus has 4 electrons available for covalent or dative bonding.

Hydrocarbons are hydrophobic and are lipids.

Some hydrocarbons also are abundant in the solar system. Lakes of liquid methane and ethane have been found on Titan, Saturn's largest moon, confirmed by the Cassini-Huygens Mission. Hydrocarbons are also abundant in nebulae forming polycyclic aromatic hydrocarbons - PAH compounds.

The bond are always non-polar.

Each hydrocarbon has a different non polarity. So, between alkane, alkene and alkyne has a different non-polar.

Polarity in the chemical bond is a state where electrons are not evenly spread distribution or the electron is more likely tied to one atom. Polarity related to  electronegative and molecular shape. In terms of polarity of a compound depends on the price of dipole moment. Dipole moment is electronegative price difference between bonded atoms.

so, non-polarity is a state where the electron difficult to bond. 

Polarity level:

alkane > alkene > alkyne

it depends on the number of bonds on the carbon chain (single, double, triple). Properties of  non polarity also depend on the geometry (shape) molecules.