Filipino BBQ goodness: puto (rice muffins)

                                                                                                                                                      

Some of the early Some of the early researchers in organic researchers in organic

chemistry became intriguedchemistry became intrigued by by fragrant oils fragrant oils that could that could be extracted from certain be extracted from certain plants. The compounds plants. The compounds

responsible for theresponsible for the aromas, aromas, had similar chemical had similar chemical

properties. As a result, they properties. As a result, they werewere groupedgrouped together and together and

calledcalled AROMATICS AROMATICS COMPOUNDS.COMPOUNDS.

As more and more aromatic As more and more aromatic compounds werecompounds were isolatedisolated and and

studied, chemist gradually studied, chemist gradually realized that aromatic realized that aromatic

contained contained six carbon six carbon atoms atoms and had low and had low hydrogen – to – hydrogen – to –

carbon carbon ratios (relative to other ratios (relative to other hydrocarbon). They also hydrocarbon). They also realized that the term realized that the term

aromatic was aromatic was notnot always always accurate. Because there are accurate. Because there are

many many fragrant compounds fragrant compounds do do not have not have aromatic properties. aromatic properties.

Kekule was to say later that he must have dozed off Kekule was to say later that he must have dozed off at this point. In his at this point. In his dream the black balls of carbon the black balls of carbon turned into turned into black impsblack imps with forked tails that began with forked tails that began racing around the room and would soon be upsetting racing around the room and would soon be upsetting the apparatus of the laboratory. He was ready to run the apparatus of the laboratory. He was ready to run the rascals out. Then, almost suddenly, the confusion the rascals out. Then, almost suddenly, the confusion

died away as each imp grabbed the tail of the one died away as each imp grabbed the tail of the one ahead of him, the ahead of him, the six formingsix forming a whirling circle. One a whirling circle. One

hand of each imp held a tail, the other a white hand of each imp held a tail, the other a white handkerchief--and they waved to him as the group handkerchief--and they waved to him as the group

whirled by. He said that he came awake with a start, whirled by. He said that he came awake with a start, realizing that the imps were acting out the realizing that the imps were acting out the formula formula for benzenefor benzene. As his hand grabbed the sketching . As his hand grabbed the sketching

pencil, the imps were back to black balls again and pencil, the imps were back to black balls again and the handkerchiefs had changed to hydrogen atoms. the handkerchiefs had changed to hydrogen atoms.

How simple the arrangement turned out to be. How simple the arrangement turned out to be.

““The carbon atoms of benzene form The carbon atoms of benzene form a ring."a ring."

Modern benzene Modern benzene structurestructure

NomenclNomenclatureature

•When a When a single hydrogen single hydrogen of the benzene ring is of the benzene ring is

replaced, the compound replaced, the compound can be named as a can be named as a

derivative of benzenederivative of benzene. .

CH2CH3

ethylbenzene

Br

bromobenzene

Cl chlorobenzen

eNO2

nitrobenzene

•A number of benzene A number of benzene derivatives are known by derivatives are known by common names common names that are that are also also IUPAC – accepted IUPAC – accepted

and are used and are used preferentially over other preferentially over other

possibilities.possibilities.

CH3

Toluene

OH

Phenol

NH2

Aniline

C — OH

║

O

Benzoic Acid

O ║ C – CH3

O ║ C

O ║ C – H

•Compounds formed by replacing a hydrogen of

benzene with more complex hydrocarbon group can be named by designating the

benzene ring as substituent.

•We called them phenyl group.

•benzyl

CH3CHCH ═ CH2

3 – phenyl – 1 – butene

CH3 — C — C — C — CH3

ا ا ا

اا ا

Br

Br3HC

3HC

2,2 – dibromo – 4,4 – dimethyl – 3,3 – diphenylpentane

CH2

OH

Cl2 – benzyl – 4 – chlorophenol

• When When two groups two groups are are attached to a benzene ring, attached to a benzene ring, three isomeric structures three isomeric structures are possible. They can be are possible. They can be

designated by the prefixes designated by the prefixes orthoortho ( (oo), ), metameta ( (mm), and ), and parapara

((pp):):

ClBr

O - bromochlorobenzene

CO2

H

NO2

m – nitrobenzoic acid

CH3

Clp - chlorotoluene

CH3 CH3 CH3

CH3

CH3

CH31,2 – dimethylbenzene

O – xylene 1,3 - dimethylbenzene

m – xylene

1,4 - dimethylbenzene

p - xylene

• When When two or more groups two or more groups are are attached to a benzene ring, their attached to a benzene ring, their

positions can be indicated by positions can be indicated by numbering the carbon atoms of the numbering the carbon atoms of the

ring so as to ring so as to obtain the lowest obtain the lowest possible numbers possible numbers for the for the

attachment positions. attachment positions.

• Group that comes first in Group that comes first in alphabeticalalphabetical orderorder is given the is given the

lower number.lower number.

BrCl

I

O2N NO2

OH

NO2

CH3

NO2

Br

1 – bromo – 2 – chloro – 4 – iodobenzene

2,4,6 – trinitrophenol

3 – bromo – 5 - nitrotoluene

NO2

NO2 NO21,3,5 –

trinitrobenzene

CH3

NO2

2ON NO2

2,4,6 - trinitrotoluene

TNT

Preparation•Major sources of aromatic Major sources of aromatic

compounds are petroleum compounds are petroleum and coal tar – (a sticky, and coal tar – (a sticky, dark – colored material dark – colored material derived from coal.derived from coal.

•Natural sourcesNatural sources

•Can be synthesize Can be synthesize synthetically synthetically

PhysicalPhysicalPropertiesProperties

Physical Physical PropertiesProperties•Similar to those of Similar to those of

ALKANES & ALKENESALKANES & ALKENES

•Non – PolarNon – Polar

•Insoluble in water Insoluble in water (hydrophobic)(hydrophobic)

•FlammableFlammable

•Low density in waterLow density in water

ChemicaChemicall

PropertiesProperties

Benzene Benzene ReactionsReactions•Halogenation Halogenation

•NitrationNitration

•SulfonationSulfonation

•AlkylationAlkylation

Industrial Industrial ApplicationApplication

ss

MedicineMedicine

MedicineMedicine

AntisepticAntiseptic

Consumer Consumer ProductsProducts

DisinfectanDisinfectantt

Synthetic Synthetic FiberFiber

PlasticPlastic

PreservativPreservativeses

DyesDyes

Fuel Fuel AdditivesAdditives

– – finfin – –