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46-559: A Curry house may refer to a restaurant serving South Asian cuisine , particularly in the UK, Australia, and Europe. Curry House may also refer to: In the United States (by state then city) South Asian cuisine Chapati , a type of flat bread , is a common part of meals to be had in many parts of the subcontinent. Other staples from many of the cuisines include rice, roti made from atta flour , and beans. Foods in this area of

92-400: A Wheland intermediate , in which (fourth) the conjugation of the ring is broken. He introduced the symbol C centered on the ring as a shorthand for the inner cycle , thus anticipating Erich Clar 's notation. It is argued that he also anticipated the nature of wave mechanics , since he recognized that his affinities had direction, not merely being point particles, and collectively having

138-440: A chemical characteristic in common, namely higher unsaturation indices than many aliphatic compounds , and Hofmann may not have been making a distinction between the two categories. In the 19th century chemists found it puzzling that benzene could be so unreactive toward addition reactions, given its presumed high degree of unsaturation. The cyclohexatriene structure for benzene was first proposed by August Kekulé in 1865. Over

184-406: A cyclic system of molecular orbitals, formed from p π atomic orbitals and populated in a closed shell by 4n (n is an integer) electrons, is given a single half-twist to correspond to a Möbius strip . A π system with 4n electrons in a flat (non-twisted) ring would be anti-aromatic, and therefore highly unstable, due to the symmetry of the combinations of p atomic orbitals. By twisting the ring,

230-432: A distribution that could be altered by introducing substituents onto the benzene ring ( much as the distribution of the electric charge in a body is altered by bringing it near to another body ). The quantum mechanical origins of this stability, or aromaticity, were first modelled by Hückel in 1931. He was the first to separate the bonding electrons into sigma and pi electrons. An aromatic (or aryl ) compound contains

276-412: A manifestation of cyclic delocalization and of resonance . This is usually considered to be because electrons are free to cycle around circular arrangements of atoms that are alternately single- and double- bonded to one another. These bonds may be seen as a hybrid of a single bond and a double bond, each bond in the ring identical to every other. This commonly seen model of aromatic rings, namely

322-449: A new, weakly bonding orbital (and also creates a weakly antibonding orbital). Hence, cyclobutadiene is non-aromatic; the strain of the asymmetric configuration outweighs the anti-aromatic destabilization that would afflict the symmetric, square configuration. Aromatic compounds play key roles in the biochemistry of all living things. The four aromatic amino acids histidine , phenylalanine , tryptophan , and tyrosine each serve as one of

368-515: A result of Mughal legacy, Pakistan also mutually inherited many recipes and dishes from that era alongside the Indian Republic. Regional cuisines include: Other Pakistani cuisine include: Sri Lankan cuisine has been shaped by many historical, cultural, and other factors. Foreign traders who brought new food items; influences from Malay cuisine and South Indian cuisine are evident. Aromatic In organic chemistry , aromaticity

414-427: A set of covalently bound atoms with specific characteristics: Whereas benzene is aromatic (6 electrons, from 3 double bonds), cyclobutadiene is not, since the number of π delocalized electrons is 4, which of course is a multiple of 4. The cyclobutadienide (2−) ion, however, is aromatic (6 electrons). An atom in an aromatic system can have other electrons that are not part of the system, and are therefore ignored for

460-534: A variety of cuisines based upon ethnicity , soil and climate relating to Nepal's cultural diversity and geography . Dal-bhat-tarkari ( Nepali : दाल भात तरकारी ) is eaten throughout Nepal. Nepali cuisine has significant influences from Neighboring Indian and Tibetan cuisines . Nepalese cuisine includes: Pakistani cuisine ( Urdu : پاکستانی پکوان ) is part of the greater South Asian with significant influence from West Asian cuisines and Central Asian cuisines due to its geographic location and influence. As

506-495: A way of serving utensils in a proper manner. Bengali cuisine has the only traditionally developed multi-course tradition from the subcontinent that is analogous in structure to the modern service à la russe style of French cuisine , with food served course-wise rather than all at once. Bhutanese cuisine employs a lot of red rice (like brown rice in texture, but with a nutty taste, the only variety of rice that grows at high altitudes), buckwheat, and increasingly maize. The diet in

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552-478: Is a chemical property describing the way in which a conjugated ring of unsaturated bonds , lone pairs , or empty orbitals exhibits a stabilization stronger than would be expected by the stabilization of conjugation alone. The earliest use of the term was in an article by August Wilhelm Hofmann in 1855. There is no general relationship between aromaticity as a chemical property and the olfactory properties of such compounds. Aromaticity can also be considered

598-880: Is an even number, such as cyclotetradecaheptaene . In heterocyclic aromatics ( heteroaromats ), one or more of the atoms in the aromatic ring is of an element other than carbon. This can lessen the ring's aromaticity, and thus (as in the case of furan ) increase its reactivity. Other examples include pyridine , pyrazine , imidazole , pyrazole , oxazole , thiophene , and their benzannulated analogs ( benzimidazole , for example). Polycyclic aromatic hydrocarbons are molecules containing two or more simple aromatic rings fused together by sharing two neighboring carbon atoms (see also simple aromatic rings ). Examples are naphthalene , anthracene , and phenanthrene . Many chemical compounds are aromatic rings with other functional groups attached. Examples include trinitrotoluene (TNT), acetylsalicylic acid (aspirin), paracetamol , and

644-454: Is characterized by a wide assortment of dishes and cooking techniques. As a consequence, Indian cuisine varies from region to region, reflecting the varied demographics of the ethnically diverse subcontinent. India's religious beliefs and culture has played an influential role in the evolution of its cuisine. It has influences from Middle Eastern cuisine , Southeast Asian cuisine , East Asian cuisine and Central Asian cuisine , as well as

690-463: Is dominated by Bengali cuisine and has been shaped by the diverse history and riverine geography of Bangladesh . The country has a tropical monsoon climate . Rice is the main staple food of Bangladeshi people and it is served with a wide range of curries . Bangladeshi dishes exhibit strong aromatic flavours; and often include eggs , potatoes , tomatoes and aubergines . A variety of spices and herbs , along with mustard oil and ghee ,

736-565: Is found in homoaromaticity where conjugation is interrupted by a single sp ³ hybridized carbon atom. When carbon in benzene is replaced by other elements in borabenzene , silabenzene , germanabenzene , stannabenzene , phosphorine or pyrylium salts the aromaticity is still retained. Aromaticity also occurs in compounds that are not carbon-based at all. Inorganic 6-membered-ring compounds analogous to benzene have been synthesized. Hexasilabenzene (Si 6 H 6 ) and borazine (B 3 N 3 H 6 ) are structurally analogous to benzene, with

782-409: Is indeed the earliest introduction of the term, it is curious that Hofmann says nothing about why he introduced an adjective indicating olfactory character to apply to a group of chemical substances only some of which have notable aromas. Also, many of the most odoriferous organic substances known are terpenes , which are not aromatic in the chemical sense. But terpenes and benzenoid substances do have

828-534: Is less common in India , Nepal and Sri Lanka than in other South Asian cuisines because cattle have a special place in Dharmic religions . Prohibitions against beef extend to the meat of (water) buffalo and yaks to some extent. Pork is considered as a taboo food item by all Muslims and is not taboo but avoided by many Hindus, though it is commonly eaten in some regions like Northeast India and Goa where Christianity

874-551: Is native to India, was often used by 400 A.D. The Greeks brought saffron and the Chinese introduced tea. The Portuguese and British made red chili, potato and cauliflower popular after 1700 A.D. Mughals , who began arriving in India after 1200, saw food as an art and many of their dishes are cooked with as many as 25 spices. They also used rose water, cashews, raisins, and almonds. In the late 18th and early 19th century, an autobiography of

920-464: Is shared by all six in the ring. Thus, there are not enough electrons to form double bonds on all the carbon atoms, but the "extra" electrons strengthen all of the bonds on the ring equally. The resulting molecular orbital has π symmetry. [REDACTED] The first known use of the word "aromatic" as a chemical term — namely, to apply to compounds that contain the phenyl radical — occurs in an article by August Wilhelm Hofmann in 1855. If this

966-438: Is standard for resonance diagrams , a double-headed arrow is used to indicate that the two structures are not distinct entities, but merely hypothetical possibilities. Neither is an accurate representation of the actual compound, which is best represented by a hybrid (average) of these structures, which can be seen at right. A C=C bond is shorter than a C−C bond, but benzene is perfectly hexagonal—all six carbon-carbon bonds have

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1012-1079: Is used in Bangladeshi cooking. The main breads are naan , porota , roti , bakarkhani and luchi . Dal is the second most important staple food which is served with rice/porota/luchi. Fish is a staple in Bangladeshi cuisine, especially freshwater fish , which is a distinctive feature of the country's gastronomy. Major fish dishes include ilish ( hilsa ) , pabda ( butterfish ), rui ( rohu ), pangash ( pangas catfish ), chitol ( clown knifefish ), magur ( walking catfish ), bhetki ( barramundi ) and tilapia . Meat consumption includes beef , lamb , venison , chicken , duck , squab and koel . Vegetable dishes, either mashed ( bhorta ), boiled ( sabji ), or leaf-based ( saag ), are widely served. Seafood such as lobsters and shrimps are also often prevalent. Islamic dietary laws are prevalent across Bangladesh. Halal foods are food items that Muslims are allowed to eat and drink under Islamic dietary guidelines. The criteria specifies both what foods are allowed, and how

1058-418: Is wide-spread. A variety of very sweet desserts which use dairy products is also found in cuisines of the subcontinent. The main ingredients in desserts of the subcontinent are reduced milk, ground almonds, lentil flour, ghee and sugar. Kheer is a dairy-based rice pudding, a common dessert. Many foods from the subcontinent have been known for over five thousand years. The Indus Valley people, who settled in

1104-530: The Mediterranean cuisines due to the historical and contemporary cross-cultural interactions with these neighboring regions. Regional cuisine includes: Maldivian cuisine, also called Dhivehi cuisine, is the cuisine of the Nation of Maldives and of Minicoy , India . The traditional cuisine of Maldivians is based on three main items and their derivatives: coconuts, fish and starches. Nepalese cuisine comprises

1150-677: The 20 basic building-blocks of proteins. Further, all 5 nucleotides ( adenine , thymine , cytosine , guanine , and uracil ) that make up the sequence of the genetic code in DNA and RNA are aromatic purines or pyrimidines . The molecule heme contains an aromatic system with 22 π electrons. Chlorophyll also has a similar aromatic system. Aromatic compounds are important in industry. Key aromatic hydrocarbons of commercial interest are benzene , toluene , ortho -xylene and para -xylene . About 35 million tonnes are produced worldwide every year. They are extracted from complex mixtures obtained by

1196-492: The 4n + 2 rule. In furan , the oxygen atom is sp² hybridized. One lone pair is in the π system and the other in the plane of the ring (analogous to C-H bond on the other positions). There are 6 π electrons, so furan is aromatic. Aromatic molecules typically display enhanced chemical stability, compared to similar non-aromatic molecules. A molecule that can be aromatic will tend to alter its electronic or conformational structure to be in this situation. This extra stability changes

1242-583: The Scottish Robert Lindsay mentions a Sylheti man called Saeed Ullah cooking a curry for Lindsay's family. This is possibly the oldest record of Indian cuisine in the United Kingdom . Afghan cuisine is influenced by Persian, Central Asian, and Indian cuisines due to Afghanistan's close proximity and cultural ties. The cuisine is halal and mainly based on mutton , beef , poultry and fish with rice and Afghan bread . Bangladeshi cuisine

1288-449: The carbon atoms replaced by another element or elements. In borazine, the boron and nitrogen atoms alternate around the ring. Quite recently, the aromaticity of planar Si 5 rings occurring in the Zintl phase Li 12 Si 7 was experimentally evidenced by Li solid state NMR. Metal aromaticity is believed to exist in certain metal clusters of aluminium. Möbius aromaticity occurs when

1334-474: The carbon nuclei — these are called σ-bonds . Double bonds consist of a σ-bond and a π-bond. The π-bonds are formed from overlap of atomic p-orbitals above and below the plane of the ring. The following diagram shows the positions of these p-orbitals: [REDACTED] Since they are out of the plane of the atoms, these orbitals can interact with each other freely, and become delocalized. This means that, instead of being tied to one atom of carbon, each electron

1380-438: The chemistry of the molecule. Aromatic compounds undergo electrophilic aromatic substitution and nucleophilic aromatic substitution reactions, but not electrophilic addition reactions as happens with carbon-carbon double bonds. Many of the earliest-known examples of aromatic compounds, such as benzene and toluene, have distinctive pleasant smells. This property led to the term "aromatic" for this class of compounds, and hence

1426-479: The food must be prepared. The foods addressed are mostly types of meat allowed in Islam. Bangladeshi people follow certain rules and regulations while eating. It includes warm hospitality and particular ways of serving as well. This is known as Bangaliketa ( Bengali : বাঙালি কেতা ). The culture also defines the way to invite people to weddings and for dinner. Gifts are given on certain occasions. Bangaliketa also includes

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1472-420: The hills also includes chicken, yak meat, dried beef, pork, pork fat, and mutton. It has many similarities with Tibetan cuisine . Indian cuisine is characterized by its sophisticated and subtle use of many Indian spices . There is also the widespread practice of vegetarianism across its society although, overall a minority. Indian cuisine is one of the world's most diverse cuisines, each family of this cuisine

1518-454: The idea that benzene was formed from a six-membered carbon ring with alternating single and double bonds (cyclohexatriene), was developed by Kekulé (see History section below). The model for benzene consists of two resonance forms, which corresponds to the double and single bonds superimposing to give rise to six one-and-a-half bonds. Benzene is a more stable molecule than would be expected without accounting for charge delocalization. As

1564-449: The inner cycle of affinity suffers disruption, the contiguous carbon-atoms to which nothing has been attached of necessity acquire the ethylenic condition". Here, Armstrong is describing at least four modern concepts. First, his "affinity" is better known nowadays as the electron , which was to be discovered only seven years later by J. J. Thomson. Second, he is describing electrophilic aromatic substitution , proceeding (third) through

1610-419: The next few decades, most chemists readily accepted this structure, since it accounted for most of the known isomeric relationships of aromatic chemistry. Between 1897 and 1906, J. J. Thomson , the discoverer of the electron, proposed three equivalent electrons between each carbon atom in benzene. An explanation for the exceptional stability of benzene is conventionally attributed to Sir Robert Robinson , who

1656-654: The northwestern subcontinent, hunted turtles and alligator. They also collected wild grains, herbs and plants. Many foods and ingredients from the Indus period (c. 3300–1700 B.C.) are still common today. Some consist of wheat, barley, rice, tamarind, eggplant, and cucumber. The Indus Valley people cooked with oils, ginger, salt, green peppers, and turmeric root, which would be dried and ground into an orange powder. Indians have used leafy vegetables, lentils, and milk products such as yogurt and ghee throughout their history. They also used spices such as cumin and coriander. Black pepper, which

1702-427: The nucleotides of DNA . Aromaticity is found in ions as well: the cyclopropenyl cation (2e system), the cyclopentadienyl anion (6e system), the tropylium ion (6e), and the cyclooctatetraene dianion (10e). Aromatic properties have been attributed to non-benzenoid compounds such as tropone . Aromatic properties are tested to the limit in a class of compounds called cyclophanes . A special case of aromaticity

1748-422: The refining of oil or by distillation of coal tar, and are used to produce a range of important chemicals and polymers, including styrene , phenol , aniline , polyester and nylon . The overwhelming majority of aromatic compounds are compounds of carbon, but they need not be hydrocarbons. Benzene , as well as most other annulenes ( cyclodecapentaene excepted) with the formula C n H n where n ≥ 4 and

1794-554: The ring atoms of one molecule are attracted to the slight negative charge of the aromatic system on another molecule. Planar monocyclic molecules containing 4n π electrons are called antiaromatic and are, in general, destabilized. Molecules that could be antiaromatic will tend to alter their electronic or conformational structure to avoid this situation, thereby becoming non-aromatic. For example, cyclooctatetraene (COT) distorts itself out of planarity, breaking π overlap between adjacent double bonds. Relatively recently, cyclobutadiene

1840-427: The same length , intermediate between that of a single and that of a double bond . A better representation is that of the circular π bond (Armstrong's inner cycle ), in which the electron density is evenly distributed through a π-bond above and below the ring. This model more correctly represents the location of electron density within the aromatic ring. The single bonds are formed with electrons in line between

1886-403: The same mechanism, the signals of protons located near the ring axis are shifted up-field. Aromatic molecules are able to interact with each other in so-called π-π stacking : The π systems form two parallel rings overlap in a "face-to-face" orientation. Aromatic molecules are also able to interact with each other in an "edge-to-face" orientation: The slight positive charge of the substituents on

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1932-445: The symmetry of the system changes and becomes allowed (see also Möbius–Hückel concept for details). Because the twist can be left-handed or right-handed , the resulting Möbius aromatics are dissymmetric or chiral . As of 2012, there is no proof that a Möbius aromatic molecule was synthesized. Aromatics with two half-twists corresponding to the paradromic topologies were first suggested by Johann Listing . In carbo-benzene

1978-446: The term "aromaticity" for the eventually discovered electronic property. The circulating π electrons in an aromatic molecule produce ring currents that oppose the applied magnetic field in NMR . The NMR signal of protons in the plane of an aromatic ring are shifted substantially further down-field than those on non-aromatic sp² carbons. This is an important way of detecting aromaticity. By

2024-537: The world are flavoured with various types of chilli, black pepper, cloves, and other strong herbs and spices along with the flavoured butter ghee . Ginger is an ingredient that can be used in both savory and sweet recipes in cuisines from the subcontinent. Chopped ginger is fried with meat and pickled ginger is often an accompaniment to boiled rice. Ginger juice and ginger boiled in syrup are used to make desserts. Turmeric and cumin are often used to make curries. Common meats include lamb, goat, fish, chicken and beef . Beef

2070-403: Was apparently the first (in 1925) to coin the term aromatic sextet as a group of six electrons that resists disruption. In fact, this concept can be traced further back, via Ernest Crocker in 1922, to Henry Edward Armstrong , who in 1890 wrote "the (six) centric affinities act within a cycle...benzene may be represented by a double ring ( sic ) ... and when an additive compound is formed,

2116-403: Was discovered to adopt an asymmetric, rectangular configuration in which single and double bonds indeed alternate; there is no resonance and the single bonds are markedly longer than the double bonds, reducing unfavorable p-orbital overlap. This reduction of symmetry lifts the degeneracy of the two formerly non-bonding molecular orbitals, which by Hund's rule forces the two unpaired electrons into

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