Ppt Ik Hidrogen

8/10/2019 Ppt Ik Hidrogen

1/31

Kelompok 3 :

Fachri rachmat

Afinannisa ikhsan

Idzni qisthinaCitra hesti widyowati

Fauzan arif billah

Hydrogen Bonding


2/31

Hydrogen bonding

When hydrogen is bonded to a highly

electronegative atom (such as nitrogen,

oxygen, fluorine), the bonding electron pair is

drawn towards the electronegativeatom


3/31

Hydrogen bonding

Hydrogen has no inner shellelectron and is

very small in size, the positive charge density

developed is high

The nucleus of hydrogen atom is exposed toattraction by nearby electron cloud, a lone

pair electronson the electronegative atom

F H F H.....

- + - +


4/31

Hydrogen bonding

Definition:

Electrostatic attractionbetween hydrogen

atoms bonded to small, strongly electronegative

atoms (N, O and F) and the lone pair electronson these electronegative atoms

F H F H.....

- + - +

Hydrogen bonding


5/31

Hydrogen Bonding

Essential requirements for formation of

hydrogen bond:

A hydrogen atom must be directly bonded to a

highly electronegative atom(e.g. F, O and N) Anunbondedpair of electrons (lone pair

electrons)is presented on the electronegative

atom


6/31

Hydrogen bonding

Examples


7/31

Special Notes

Intermolecularhydrogen bond:

Hydrogen bond formed between twomolecules

Intramolecularhydrogen bond:

Hydrogen bond formed between

two different atoms in the

same molecule

Intermolecular hydrogen bond is strongerthan van der Waals forces

N

O

O

O

H


8/31

Importance of Hydrogen Bonding

in Physical Phenomena

Anomalous Properties of the second period

hydrides

Questions:

1. Why do H2O, NH3and HF haveabnormally highboiling point?

2. Explain why theorder of boiling pointis H2O > HF > NH3.


9/31

Q1: Why do NH3, H2O and HF

have abnormally high boiling point?

Explanation:

N, O and F are highly electronegativeatoms

Formation of intermolecular hydrogen bonds in their

hydrides. Intermolecular hydrogen bonds are much

strongerthan van der Waals forces

More energy is needed to break the hydrogen

bonds in NH3, H2O and HF


10/31

Hydrogen Bonding in HydrogenFluoride

Fluorine atoms have three electron lonepairs for bonding to other HF molecules


11/31

Q2: Explain why the order of

boiling point is H2O > HF > NH3 Explanation

H2O can form 2hydrogen bond per molecule

NH3and HF can form only 1hydrogen bond permolecule

The boiling point of H2O is higher than NH3and HF

No. of H

atoms

available for

hydrogen

bond

formation

No. of lone

pair

electrons

available

No. of

hydrogen

bonds can

form per

molecule

NH3 3 1 1

H2O 2 2 2

HF 1 3 1


12/31

Q2: Explain why the order of

boiling point is H2O > HF > NH3

Comparing N and F, Fis more electronegative

The intermolecular hydrogen bond formed

between HFmolecules is stronger than NH3

HF has a higher boiling point than NH3


13/31



Enthalpy of vaporization

Energy required to vaporized one mole of liquid

Question:Explain why H2O has thelargest enthalpy of

vaporization than H2S, H2Seand H2Te.


14/31

Explanation:

In H2O, there are intermolecular hydrogen

bonds between molecules

However, in H2S, H2Se and H2Te, the interactionbetween molecules is dipole-dipole

interactions

The strength of hydrogen bond is strongerthan

dipole-dipole interactions

To break the hydrogen bonds, moreenergy is

required

H2O has the largest enthalpy change of

vaporization


15/31


16/31

Alcohols of low molecular masses are soluble

in water because they can form

intermolecular hydrogen bonds with water

molecules


17/31



Dimerization of Carboxylic Acid

It happens when carboxylic acids are dissolved in

non-polarsolvents or in vapourstate

E.g. Ethanoic acid (CH3COOH) Ethanoic acid molecules form

dimersthrough the formation

of intermolecular hydrogen

bonds


18/31

How do these two molecules differ in boilingpoint, viscosity and water solubility? Explainwhy


19/31


in Biochemistry

Hydrogen bonding in ice and water

Intermolecular hydrogen bonds exist in both

water and ice

In water, molecules are in constant motion.Intermolecular hydrogen bondsare formed and

broken continuously.

The arrangement of

molecules is random


20/31

In ice, the molecular motion is restricted. The

molecules are arranged in a way to form the

maximumnumber of hydrogen bonds


21/31

This section of water is frozen This section of water is liquid


22/31

Each H2O molecule is tetrahedrally

bonded to 4 other H2O molecules by

hydrogen bonds

Creates an open structure and gives rise

to a lowerdensity of ice than water

Insulates the water below and prevents

complet solidification

keep fishsurvive in polar regions


23/31

The ice structure has large empty spaces whichgives it a lower density than water.


24/31

Youtube video clip

(Why do ice float?)
http://localhost/var/www/apps/conversion/tmp/scratch_3/Video/1%20Why%20does%20ice%20float%20in%20water-%20-%20George%20Zaidan%20and%20Charles%20Morton%20can%20running.mp4


25/31


in Biochemistry

Hydrogen Bonding in Proteins

The building block of protein is amino acid

NH2

R

H

COOH

R: a hydrogen atomor an alkyl group

NH2: amine group

COOH: carboxylicacid group


26/31

The combination of two amino acids will form adipeptide

The primary structure of protein is a polypeptide,which is a polymer of amino acids

Polypeptide chains form a helical structurebetween N-H and C=O groups Creates the secondary structure of protein

NH2

R

H

COOH NH2

R

H

COOH NH

2

R

H

O

N

H

R

H

COOH

+

condensation

Peptide bond


27/31

Secondary Structure of Protein


28/31

Hydrogen Bonding in DNA

DNA stands for Deoxyribose Nucleic Acid

DNA contains genetic information

Consists of 2macromolecular strands spirallingaround each other in the form of a double helix


29/31


30/31

The two nucleic acid chains are held together

by hydrogen bonds, that are formed between

specific pairs of bases on the chains

Hydrogen bonds of base pairs in DNA:AdenineThymine

CytosineGuanine


31/31

Documents

Ppt Ik Hidrogen